Wireless charging method and apparatus therefor

ABSTRACT

A wireless charging method in a wireless power transmitter, the method including sensing an object in a charging region, measuring a quality factor value, receiving information including a reference quality factor value, detecting a foreign object using the measured quality factor value and the reference quality factor value, and transmitting a response signal that includes ACK information or NAK information depending on whether or not the foreign object is detected. Further, the wireless power transmitter transmits information including a first guaranteed power value when the response signal includes the ACK information, and transmits information including a second guaranteed power value when the response signal includes the NAK information, and the first guaranteed power value is greater than the second guaranteed power value.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is Continuation of application Ser. No. 16/761,199filed on May 1, 2020 (now U.S. Pat. No. 11,437,849 issued on Sep. 6,2022), which is the National Phase of PCT/KR2018/013258 filed on Nov. 2,2018, which claims priority under 35 U.S.C. § 119(a) to PatentApplication No. 10-2017-0145585 and 10-2017-0148699 filed in theRepublic of Korea on Nov. 2, 2017, and Nov. 9, 2017, respectively, allof which are hereby expressly incorporated by reference into the presentapplication.

TECHNICAL FIELD

The present invention relates to a wireless power transmissiontechnology, and more particularly, to a wireless charging method andapparatus therefor.

BACKGROUND ART

A mobile phone, a notebook computer, and similar portable terminalsinclude a battery for storing electric power and a circuit for chargingand discharging the battery. To charge a battery of such a terminal,electric power has to be received from an external charger.

In general, as an example of a type of electrical connection between acharging apparatus for charging the battery with electric power and thebattery, there is a terminal supply type in which commercial power isreceived, converted to have voltage and current corresponding to thebattery, and supplied as electric energy to the battery throughterminals of the battery. Such a terminal supply type involves use of aphysical cable or electric wire. Therefore, when many pieces ofequipment of the terminal supply type are used, numerous cables occupy aconsiderable amount of workspace, are difficult to organize, and createa poor appearance. Further, the terminal supplying type may causeproblems of instantaneous discharge due to different electric potentialdifferences between the terminals, combustion and fire due to foreignobjects, natural discharge, deterioration in the lifespan andperformance of the battery, etc.

To solve these problems, there have recently been proposed a chargingsystem and control methods thereof involving a method of wirelesslytransmitting electric power (hereinafter referred to as a “wirelesscharging system”). Further, up through now, wireless charging systemshave not been a basic part of some portable terminals, and a consumerhas had to separately purchase wireless charging receiver accessories,thereby resulting in lower demands for wireless charging systems.However, it is expected that wireless charging users will rapidlyincrease and a terminal manufacturer will provide wireless charging as abasic feature in the future.

In general, the wireless charging system includes a wireless powertransmitter transfer for supplying electric energy in a wireless powertransmission manner, and a wireless power receiver for receiving theelectric energy from the wireless power transmitter and charging thebattery.

Such a wireless charging system may employ at least one wireless powertransmission manner (for example, an electromagnetic induction manner,an electromagnetic resonance manner, radio frequency (RF) wireless powertransmission manner, etc.) to transmit the electric power.

As an example, the wireless power transmission manner may use variouswireless power transmission standards based on the electromagneticinduction manner employing the principle of electromagnetic induction,in which an electromagnetic field is generated in an electric powertransmitter coil and electricity is induced in a receiver coil by theelectromagnetic field. Herein, the wireless power transmission standardsof the electromagnetic induction manner may include a wireless chargingtechnology of the electromagnetic induction manner defined in theWireless Power Consortium (WPC) or/and Power Matters Alliance (PMA).

As another example, the wireless power transmission manner may use theelectromagnetic resonance manner, in which an electromagnetic fieldgenerated by a transfer coil of the wireless power transmitter resonateswith a certain resonance frequency so that electric power may betransmitted to a wireless power receiver located nearby. Herein, theelectromagnetic resonance manner may include the wireless chargingtechnology of the resonance manner defined in the Air Fuel Alliance(formerly A4WP, Alliance for Wireless Power) standard organization, i.e.wireless charging technology standard organization.

As still another example, the wireless power transmission manner may usethe RF wireless power transmission manner, in which energy of lowelectric power is embedded in an RF signal to transmit the electricpower to a wireless power receiver located at a distance.

Meanwhile, in the wireless charging system, when a foreign objectabsorbing a magnetic field such as a metal is present between a wirelesspower transmitter and a wireless power receiver, a problem of a heatgeneration phenomenon, a decrease in charging efficiency, and anincrease in power consumption occur, and thus an accurate foreign objectdetection method is required.

SUMMARY

The present invention has been devised to solve problems of the relatedart described above, and an object of the present invention is toprovide a wireless charging method and an apparatus and system therefor.

In addition, another object of the present invention is to provide awireless charging method for determining the foreign object accurately,and an apparatus and system therefor.

In addition, still another object of the present invention is to providea wireless charging method solving a problem that wireless charging isnot performed by erroneously recognizing that a foreign object ispresent in the related art, and an apparatus and system therefor.

Technical problems to be solved in the present invention are not limitedto the above-mentioned technical problems, and other technical problemsnot mentioned will be clearly understood by a person having ordinaryskill in the art, to which the present invention pertains, from thefollowing descriptions.

In order to solve the above technical problems, a wireless chargingmethod according to an embodiment, in a wireless charging method in awireless power transmitter configured to wirelessly transmit power to awireless power receiver, includes: sensing an object in a chargingregion; measuring a quality factor value; receiving informationincluding a reference quality factor value; detecting a foreign objectusing the measured quality factor value and the reference quality factorvalue; and transmitting information including a first guaranteed powervalue when the foreign object is not detected, and transmittinginformation including a second guaranteed power value when the foreignobject is detected, wherein the first guaranteed power value may begreater than the second guaranteed power value.

In addition, the wireless charging method according to the embodimentmay include measuring an internal temperature of the wireless powertransmitter, and when the sensed temperature is less than a presettemperature for a preset period and the foreign object is detected, mayfurther include transmitting guaranteed power having a third guaranteedpower value, wherein the third guaranteed power value may be greaterthan the second guaranteed power value.

In addition, in the wireless charging method according to theembodiment, the second guaranteed power value may be a minimumguaranteed power of the wireless power transmitter.

In addition, in the wireless charging method according to theembodiment, the detecting of the foreign object may include determininga threshold quality factor value using the reference quality factorvalue, and determining that the foreign object is not detected when themeasured quality factor value is greater than or equal to the thresholdquality factor value, and determining that the foreign object isdetected when the measured quality factor value is less than thethreshold quality factor value.

In addition, in the wireless charging method according to theembodiment, the threshold quality factor value may be a value that isreduced by 10% from the reference quality factor value.

In addition, the wireless charging method according to the embodimentmay further include determining whether to perform wireless chargingwhen the foreign object is detected, and when it is determined toperform the wireless charging, information including a second guaranteedpower value may be transmitted, and when it is determined not to performthe wireless charging, the wireless charging may be stopped.

In addition, in the wireless charging method according to theembodiment, the determining of whether to perform the wireless chargingwhen the foreign object is detected may include determining anacceptable quality factor value using the threshold quality factorvalue, determining to perform the wireless charging when the measuredquality factor value is greater than or equal to the acceptable qualityfactor value, and determining not to perform the wireless charging whenthe measured quality factor value is less than the acceptable qualityfactor value.

In addition, in the wireless charging method according to theembodiment, the acceptable quality factor value may be a value that isreduced by 20% from the threshold quality factor value.

In addition, in the wireless charging method according to theembodiment, when the sensed temperature is less than a presettemperature for a preset period, the transmitting of guaranteed powerhaving the third guaranteed power value may be performed in arenegotiation phase.

In addition, in the wireless charging method according to theembodiment, when the foreign object is not detected and the informationincluding the first guaranteed power value is transmitted, a calibrationphase may be performed before transitioning to a power transfer phase,and when the foreign object is detected and the information includingthe second guaranteed power value is transmitted, it may transition tothe power transfer phase without performing the calibration phase.

A wireless charging method according to an embodiment, in a wirelesscharging method in a wireless power transmitter configured to wirelesslytransmit power to a wireless power receiver, includes: sensing an objectin a charging region; measuring a quality factor value; receivinginformation including a reference quality factor value; determiningwhether the reference quality factor value is less than 50; performingfirst foreign object detection using the measured quality factor valueand the reference quality factor value when the reference quality factorvalue is less than 50, and performing second foreign object detectionusing the measured quality factor value and the reference quality factorvalue when the reference quality factor value is greater than or equalto 50; and transmitting information including a first guaranteed powervalue when the foreign object is not detected by performing the firstforeign object detection, transmitting information including a secondguaranteed power value when the foreign object is detected by performingthe first foreign object detection, transmitting the informationincluding the first guaranteed power value when the foreign object isnot detected by performing the second foreign object detection, andstopping wireless charging when the foreign object is detected byperforming the second foreign object detection, wherein the firstguaranteed power value may be greater than the second guaranteed powervalue.

In addition, the wireless charging method according to the embodimentmay include measuring an internal temperature of the wireless powertransmitter, and when the sensed temperature is less than a presettemperature for a preset period and the foreign object is detected byperforming the first foreign object detection, may further includetransmitting guaranteed power having a third guaranteed power value,wherein the third guaranteed power value may be greater than the secondguaranteed power value.

A wireless charging apparatus according to an embodiment includes: oneor more transmission coils; a power converter configured to convert theintensity of DC power applied from the outside; a communication unitconfigured to exchange information with an external device; a sensorconfigured to measure a quality factor value; and a controllerconfigured to receive information including a reference quality factorvalue through the communication unit and perform foreign objectdetection, wherein the controller may detect a foreign object using themeasured quality factor value and the reference quality factor value,transmit information including a first guaranteed power value when theforeign object is not detected, and transmit information including asecond guaranteed power value when the foreign object is detected, andthe first guaranteed power value may be greater than the secondguaranteed power value.

In addition, in the wireless charging apparatus according to theembodiment, the sensor may measure an internal temperature of thewireless power transmitter, the controller may transmit guaranteed powerhaving a third guaranteed power value when the sensed temperature isless than a preset temperature for a preset period and the foreignobject is detected, and the third guaranteed power value may be greaterthan the second guaranteed power value.

In addition, in the wireless charging apparatus according to theembodiment, the second guaranteed power value may be a minimumguaranteed power of the wireless power transmitter.

In addition, in the wireless charging apparatus according to theembodiment, in the foreign object detection, the controller maydetermine a threshold quality factor value using the reference qualityfactor value, determine that the foreign object is not detected when themeasured quality factor value is greater than or equal to the thresholdquality factor value, and determine that the foreign object is detectedwhen the measured quality factor value is less than the thresholdquality factor value.

In addition, in the wireless charging apparatus according to theembodiment, the threshold quality factor value may be a value that isreduced by 10% from the reference quality factor value.

In addition, in the wireless charging apparatus according to theembodiment, the controller may determine whether to perform wirelesscharging when the foreign object is detected, when it is determined toperform the wireless charging, information including the secondguaranteed power value may be transmitted, and when it is determined notto perform the wireless charging, the wireless charging may be stopped.

In addition, in the wireless charging apparatus according to theembodiment, in the determining of whether to perform the wirelesscharging when the foreign object is detected, the controller maydetermine an acceptable quality factor value using the threshold qualityfactor value, determine to perform the wireless charging when themeasured quality factor value is greater than or equal to the acceptablequality factor value, and determine not to perform the wireless chargingwhen the measured quality factor value is less than the acceptablequality factor value.

In addition, in the wireless charging apparatus according to theembodiment, the acceptable quality factor value may be a value that isreduced by 20% from the threshold quality factor value.

In addition, in the wireless charging apparatus according to theembodiment, when the sensed temperature is less than a presettemperature for a preset period, the transmitting of guaranteed powerhaving the third guaranteed power value may be performed in arenegotiation phase.

In addition, in the wireless charging apparatus according to theembodiment, when the foreign object is not detected and the informationincluding the first guaranteed power value is transmitted, thecontroller may perform a calibration phase before transitioning to apower transfer phase, and when the foreign object is detected and theinformation including the second guaranteed power value is transmitted,it may transition to the power transfer phase without performing thecalibration phase.

A wireless charging apparatus according to an embodiment includes: oneor more transmission coils; a power converter configured to convert theintensity of DC power applied from the outside; a communication unitconfigured to exchange information with an external device; a sensorconfigured to measure a quality factor value; and a controllerconfigured to receive information including a reference quality factorvalue through the communication unit and determine whether the referencequality factor value is less than 50, wherein the controller may performfirst foreign object detection using the measured quality factor valueand the reference quality factor value when the reference quality factorvalue is less than 50, and may perform second foreign object detectionusing the measured quality factor value and the reference quality factorvalue when the reference quality factor value is greater than or equalto 50, and the controller may transmit information including a firstguaranteed power value when the foreign object is not detected andtransmit information including a second guaranteed power value when theforeign object is detected by performing the first foreign objectdetection, transmit the information including the first guaranteed powervalue when the foreign object is not detected and stop wireless chargingwhen the foreign object is detected by performing the second foreignobject detection, and the first guaranteed power value may be greaterthan the second guaranteed power value.

In addition, in the wireless charging apparatus according to theembodiment, the sensor may measure an internal temperature of thewireless power transmitter, the controller may transmit guaranteed powerincluding a third guaranteed power value when the sensed temperature isless than a preset temperature for a preset period and the foreignobject is detected by performing the first foreign object detection, andthe third guaranteed power value may be greater than the secondguaranteed power value.

A wireless charging method according to an embodiment, in a wirelesscharging method in a wireless power transmitter configured to wirelesslytransmit power to a wireless power receiver, includes: measuring aquality factor value prior to a ping phase; receiving a foreign objectdetection (FOD) status packet including a reference quality factor valuein a negotiation phase; determining a threshold quality factor valueusing the reference quality factor value; determining an acceptablequality factor value using the threshold quality factor value; anddetecting a first foreign object based on the measured quality factorvalue and the acceptable quality factor value.

In addition, in the wireless charging method according to theembodiment, the threshold quality factor value may be a value that isreduced by 10% from the reference quality factor value, and theacceptable quality factor value may be a value that is reduced by 20%from the threshold quality factor value.

In addition, in the wireless charging method according to theembodiment, the detecting of the first foreign object may determinewhether the measured quality factor value is greater than or equal tothe acceptable quality factor value.

In addition, the wireless charging method according to the embodimentmay further include transmitting an ACK for performing wireless chargingwhen the measured quality factor value is greater than or equal to theacceptable quality factor value.

In addition, the wireless charging method according to the embodimentmay further include determining whether the measured quality factorvalue is greater than or equal to the threshold quality factor value,and after transition to the calibration phase, performing calibrationwhen the measured quality factor value is greater than or equal to thethreshold quality factor value and not performing the calibration whenthe measured quality factor value is less than the threshold qualityfactor value.

In addition, the wireless charging method according to the embodimentmay further include performing second foreign object detection aftertransition to a power transfer phase.

In addition, in the wireless charging method according to theembodiment, in the second foreign object detection, when a power lossvalue, which is determined based on a reception power value and atransmission power value, exceeds a predetermined threshold power lossvalue, it may be determined that a foreign object is present.

In addition, in the wireless charging method according to theembodiment, in the second foreign object detection, when a measuredinternal temperature value exceeds a predetermined threshold temperaturevalue, it may be determined that the foreign object is present.

In addition, in the wireless charging method according to theembodiment, the FOD status packet may further include a reference peakfrequency value, and the wireless charging method may further includemeasuring a frequency value before the ping phase, determining athreshold frequency value using the reference peak frequency value inthe negotiation phase, and determining an acceptable frequency valueusing the threshold frequency value, wherein the detecting of the firstforeign object may be performed based on the measured frequency valueand the acceptable frequency value.

In addition, in the wireless charging method according to theembodiment, the threshold frequency value may be a value that isincreased by 10% from the reference peak frequency value, and theacceptable frequency value may be a value that is increased by 20% fromthe threshold frequency value.

In addition, in the wireless charging method according to theembodiment, the detecting of the first foreign object may determinewhether the measured frequency value is less than or equal to theacceptable frequency value.

The wireless charging method according to the embodiment may furtherinclude transmitting an ACK signal for performing wireless charging whenthe measured frequency value is less than or equal to the acceptablefrequency value.

In addition, the wireless charging method according to the embodimentmay further include determining whether the measured frequency value isless than or equal to the threshold frequency value, and aftertransition to the calibration phase, performing calibration when themeasured frequency value is less than or equal to the thresholdfrequency value and not performing the calibration when the measuredfrequency value exceeds the threshold frequency value.

In addition, in the wireless charging method according to theembodiment, the FOD status packet may further include a reference peakfrequency value, and the wireless charging method may further includemeasuring an equivalent series resistance value before the ping phase,determining a threshold equivalent series resistance value using thereference quality factor value and the reference peak frequency value inthe negotiation phase, and determining an acceptable equivalent seriesresistance value using the threshold equivalent series resistance value,wherein the detecting of the first foreign object may be performed basedon the measured equivalent series resistance value and the acceptableequivalent series resistance value.

In addition, in the wireless charging method according to theembodiment, the threshold equivalent series resistance value may be avalue that is increased by 10% from the reference equivalent seriesresistance value, and the acceptable equivalent series resistance valuemay be a value that is increased by 20% from the threshold equivalentseries resistance value.

In addition, in the wireless charging method according to theembodiment, the detecting of the first foreign object may determinewhether the measured equivalent series resistance value is less than orequal to the acceptable equivalent series resistance value.

In addition, the wireless charging method according to the embodimentmay further include transmitting an ACK for performing wireless chargingwhen the measured equivalent series resistance value is less than orequal to the acceptable equivalent series resistance value.

In addition, the wireless charging method according to the embodimentmay further include determining whether the measured equivalent seriesresistance value is less than or equal to the threshold equivalentseries resistance value, and after transition to the calibration phase,performing calibration when the measured equivalent series resistancevalue is less than or equal to the threshold equivalent seriesresistance value and not performing the calibration when the measuredequivalent series resistance value exceeds the threshold equivalentseries resistance value.

A wireless charging apparatus according to an embodiment includes: oneor more transmission coils; a power converter configured to convert theintensity of DC power applied from the outside; a communication unitconfigured to exchange information with an external device; a sensorconfigured to measure a quality factor value; and a controllerconfigured to receive an FOD status packet including a reference qualityfactor value through the communication unit and perform first foreignobject detection, wherein the controller may determine a thresholdquality factor value using the reference quality factor value anddetermine an acceptable quality factor value using the threshold qualityfactor value, and the first foreign object detection may be performedbased on the measured quality factor value and the acceptable qualityfactor value.

In addition, in the wireless charging apparatus according to theembodiment, the threshold quality factor value may be a value that isreduced by 10% from the reference quality factor value, and theacceptable quality factor value may be a value that is reduced by 20%from the threshold quality factor value.

In addition, in the wireless charging apparatus according to theembodiment, in the first foreign object detection, the controller maydetermine whether the measured quality factor value is greater than orequal to the acceptable quality factor value.

In addition, in the wireless charging apparatus according to theembodiment, the controller may transmit an ACK for performing wirelesscharging when the measured quality factor value is greater than or equalto the acceptable quality factor value.

In addition, in the wireless charging apparatus according to theembodiment, after transition to a calibration phase, the controller mayperform calibration when the measured quality factor value is greaterthan or equal to the threshold quality factor value and may not performthe calibration when the measured quality factor value is less than thethreshold quality factor value.

In addition, in the wireless charging apparatus according to theembodiment, after transition to a power transfer phase, the controllermay perform second foreign object detection.

In addition, in the wireless charging apparatus according to theembodiment, in the second foreign object detection, when a power lossvalue, which is determined based on a received power value and atransmission power value, exceeds a predetermined threshold power lossvalue, the controller may determine that a foreign object is present.

In addition, in the wireless charging apparatus according to theembodiment, in the second foreign object detection, when a measuredinternal temperature value exceeds a predetermined threshold temperaturevalue, the controller may determine that the foreign object is present.

In addition, the wireless charging apparatus according to theembodiment, the FOD status packet may further include a reference peakfrequency value, the sensor may measure a frequency value, thecontroller may determine a threshold frequency value using the referencepeak frequency value and determine an acceptable frequency value usingthe threshold frequency value, and the first foreign object detectionmay be performed based on the measured frequency value and theacceptable frequency value.

In addition, in the wireless charging apparatus according to theembodiment, the threshold frequency value may be a value that isincreased by 10% from the reference peak frequency value, and theacceptable frequency value may be a value that is increased by 20% fromthe threshold frequency value.

In addition, in the wireless charging apparatus according to theembodiment, in the first foreign object detection, the controller maydetermine whether the measured frequency value is less than or equal tothe acceptable frequency value.

In addition, in the wireless charging apparatus according to theembodiment, the controller may transmit an ACK signal for performingwireless charging when the measured frequency value is less than orequal to the acceptable frequency value.

In addition, in the wireless charging apparatus according to theembodiment, after transition to the calibration phase, the controllermay perform calibration when the measured frequency value is less thanor equal to the threshold frequency value and may not perform thecalibration when the measured frequency value exceeds the thresholdfrequency value.

In addition, the wireless charging apparatus according to theembodiment, the FOD status packet may further include a reference peakfrequency value, the sensor may measure an equivalent series resistancevalue, the controller may determine a threshold equivalent seriesresistance value using the reference quality factor value and thereference peak frequency value in a negotiation phase and determine anacceptable equivalent series resistance value using the thresholdequivalent series resistance value, and the first foreign objectdetection may be performed based on the measured equivalent seriesresistance value and the acceptable equivalent series resistance value.

In addition, in the wireless charging apparatus according to theembodiment, the threshold equivalent series resistance value may be avalue that is increased by 10% from the reference equivalent seriesresistance value, and the acceptable equivalent series resistance valuemay be a value that is increased by 20% from the threshold equivalentseries resistance value.

In addition, in the wireless charging apparatus according to theembodiment, in the first foreign object detection, the controller maydetermine whether the measured equivalent series resistance value isless than or equal to the acceptable equivalent series resistance value.

In addition, in the wireless charging apparatus according to theembodiment, the controller may transmit an ACK for performing wirelesscharging when the measured equivalent series resistance value is lessthan or equal to the acceptable equivalent series resistance value.

In addition, in the wireless charging apparatus according to theembodiment, after transition to the calibration phase, the controllermay perform calibration when the measured equivalent series resistancevalue is less than or equal to the threshold equivalent seriesresistance value and may not perform the calibration when the measuredequivalent series resistance value exceeds the threshold equivalentseries resistance value.

In addition, in order to solve the above technical problems, a wirelesscharging method according to an embodiment, in a wireless chargingmethod in a wireless power transmitter configured to wirelessly transmitpower to a wireless power receiver, includes: sensing an object in acharging region; measuring an equivalent series resistance value and apeak frequency value; receiving information including a referencequality factor value and a reference peak frequency value; determining afirst threshold equivalent series resistance value and a threshold peakfrequency value; and detecting a foreign object using the measuredequivalent series resistance value, the measured peak frequency value,the first threshold equivalent series resistance value, and thethreshold peak frequency value, wherein when the measured equivalentseries resistance value is greater than or equal to the first thresholdequivalent series resistance value and the measured peak frequency valueis greater than or equal to the threshold peak frequency value, thewireless power transmitter may determine that a foreign object ispresent and stop transmitting power.

In addition, in the wireless charging method according to theembodiment, the determining of the first threshold equivalent seriesresistance value may include determining a reference equivalent seriesresistance value using the reference quality factor value and thereference peak frequency value, and determining a value reduced by apredetermined ratio from the reference equivalent series resistancevalue as the first threshold equivalent series resistance value.

In addition, in the wireless charging method according to theembodiment, the threshold peak frequency value may be greater than thereference peak frequency value.

In addition, in the wireless charging method according to theembodiment, when the measured peak frequency value is greater than orequal to the threshold peak frequency value and the measured equivalentseries resistance value is less than or equal to the first thresholdequivalent series resistance value, information indicating that theforeign object is not detected may be transmitted to the wireless powerreceiver.

A wireless charging apparatus according to an embodiment including: aninverter configured to convert DC power into AC power; a resonancecircuit including a resonance capacitor and a transmission coil and towhich the AC power is applied; a communication unit configured todemodulate an in-band signal modulated in the wireless power receiver; asensor configured to measure a voltage of the resonance circuit; and acontroller, wherein the controller may detect an object in a chargingregion, may determine a quality factor value and a peak frequency valuebased on the voltage measured by the sensor, may receive informationincluding a reference quality factor value and a reference peakfrequency value through the communication unit, may determine a firstthreshold equivalent series resistance value and a threshold peakfrequency value, and may be set to detect a foreign object using themeasured equivalent series resistance value, the measured peak frequencyvalue, the first threshold equivalent series resistance value, and thethreshold peak frequency value, and the wireless power transmitter maydetermine that the foreign object is present and stop transmitting powerwhen the measured equivalent series resistance value is greater than orequal to the first threshold equivalent series resistance value and themeasured peak frequency value is greater than or equal to the thresholdpeak frequency value.

In addition, in the wireless charging apparatus according to theembodiment, the first threshold equivalent series resistance value maybe determined based on the reference quality factor value and thereference peak frequency value.

Advantageous Effects

Effects of a wireless charging method and an apparatus and systemtherefor according to the present invention will be described asfollows.

The present invention may provide a wireless charging method and anapparatus and system therefor.

In addition, the present invention may determine a foreign objectaccurately.

In addition, the present invention may accurately determine a foreignobject to prevent a heat generation phenomenon, a decrease in chargingefficiency, and a loss of power consumption.

In addition, the present invention may solve a problem that wirelesscharging is not performed by erroneously recognizing that a foreignobject is present in the related art.

In addition, the present invention may solve a problem in which wirelesscharging is not performed unnecessarily by determining to distinguishthat a charging distance between a wireless power transmitter and awireless power receiver is increased and presence of a foreign object.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are to help understanding of the presentinvention, and provide embodiments of the present invention inconjunction with the detailed description. However, the technicalfeatures of the present invention are not limited to specific drawings,and features disclosed in the drawings may combine with each other toform a new embodiment.

FIG. 1 is a block diagram for describing a wireless charging systemaccording to one embodiment.

FIG. 2 . is a state transition view for describing a wireless powertransmission process defined in the WPC standards.

FIG. 3 is a block diagram for describing a structure of a wireless powertransmitter according to one embodiment.

FIG. 4 is a block diagram for describing a structure of a wireless powerreceiver interworking with the wireless power transmitter of FIG. 3 .

FIG. 5 is a view for describing a wireless charging method on a wirelesscharging system according to one embodiment.

FIG. 6 is a view for describing a wireless charging method in a wirelesspower transmitter according to one embodiment.

FIG. 7 is a view for describing a foreign object detection methodaccording to a quality factor value.

FIG. 8 is a view for describing a wireless charging method in a wirelesspower transmitter according to another embodiment.

FIG. 9 is a view for describing a foreign object detection methodaccording to a frequency value.

FIG. 10 is a view for describing a wireless charging method in awireless power transmitter according to still another embodiment.

FIG. 11 is a view for describing a foreign object detection methodaccording to an equivalent series resistance value.

FIGS. 12A and 12B are views for describing a wireless charging method ina wireless power transmitter according to still another embodiment.

FIG. 13 is a view for describing a wireless charging method on awireless charging system according to still another embodiment.

FIGS. 14A and 14B are views for describing a wireless charging method ina wireless power transmitter according to still another embodiment ofFIG. 13 .

FIG. 15A is a view for describing a foreign object detection method ofthe wireless charging method of FIG. 14A.

FIG. 15B is a view describing a method of determining whether to performwireless charging in the wireless charging method of FIG. 14A.

FIG. 16 is a view for describing a wireless charging method on awireless charging system according to still another embodiment.

FIGS. 17A and 17B are views for describing a wireless charging method ina wireless power transmitter according to still another embodiment ofFIG. 16 .

FIG. 18 is a view for describing a wireless charging method in awireless power transmitter according to still another embodiment.

FIG. 19 is view for describing a wireless charging method on a wirelesscharging system according to still another embodiment.

FIG. 20 is a view for describing a wireless charging method in awireless power transmitter according to still another embodiment of FIG.19 .

FIG. 21 is a view for describing a foreign object detection methodaccording to a quality factor value in FIG. 20 .

FIG. 22 is a view for describing a wireless charging method on awireless charging system according to still another embodiment.

FIG. 23 is a view for describing a wireless charging method in awireless power transmitter according to another embodiment of FIG. 22 .

FIG. 24 is a view for describing a foreign object detection methodaccording to an equivalent series resistance value.

FIG. 25 is a view for describing a wireless charging method on awireless charging system according to still another embodiment.

FIG. 26 is a view for describing a wireless charging method in awireless power transmitter according to still another embodiment of FIG.25 .

FIG. 27 is a view for describing a foreign object detection methodaccording to a frequency value.

FIG. 28 is a view for describing a wireless charging method on awireless charging system according to still another embodiment.

FIG. 29 is a view for describing a wireless charging method in awireless power transmitter according to another embodiment of FIG. 28 .

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, apparatus and various methods according to embodiments willbe described in detail with reference to the accompanying drawings.Suffixes “module” and “part” for elements used in the followingdescriptions are given or used just for convenience in writing thespecification, and do not have meanings or roles distinguishable betweenthem.

Although all elements described in above embodiments are combined intoone or operate as they are combined, the present disclosure is notlimited to the embodiments. In other words, one or more elements amongall of them may be selectively combined and operate without departingfrom the scope of the present disclosure. Further, all the elements maybe respectively materialized as single independent hardware components,but some or all of them may be selectively combined and materialized asa computer program having a program module to perform some or allfunctions combined in a single or plural hardware components. Codes andcode segments of the computer program may be easily conceived by aperson having an ordinary skill in the art. Such a computer program maybe stored in computer readable media, and read and executed by acomputer, thereby materializing the embodiments. The medium for storingthe computer program may include a magnetic recording medium, an opticalrecording medium, a carrier wave medium, etc.

In describing the embodiments, when elements are described with terms“above (up) or below (down)”, “front (head) or back (rear)”, the terms“above (up) or below (down)”, “front (head) or back (rear)” may refer tomeanings of direct contact between two elements or one or more elementsinterposed between the two elements.

Further, it will be understood that the term “include”, “comprise” or“have”, etc. used as above means a presence of an element unlessotherwise stated, and does not preclude the presence or addition of oneor more other elements. Unless otherwise defined, all terms includingtechnical and scientific terms used herein have the same meaning ascommonly understood by one of ordinary skill in the art to which thisinvention pertains. It will be further understood that terms, such asthose defined in commonly used dictionaries, should be interpreted ashaving a meaning that is consistent with their meaning in the context ofthe relevant art and will not be interpreted in an idealized or overlyformal sense unless expressly so defined here.

Further, elements of the present disclosure may be described with termsfirst, second, A, B, (a), (b), etc. These terms are only used todistinguish one element from another, and do not limit the element's ownmeaning, sequence, order, etc. It will be understood that when anelement is referred to as being “connected”, “combined” or “coupled” toanother element, it may be directly connected or coupled to the otherelement or intervening elements may be “connected”, “combined” or“coupled” between the elements.

Further, in the present disclosure, detailed descriptions of the relatedwell-known art may be omitted when the well-known art is obvious tothose skilled in the art and may cloud the gist of the presentdisclosure.

In describing embodiments, an apparatus for wirelessly transmittingelectric power in a wireless power charging system may be also called awireless power transmitter, a wireless power transmission apparatus, atransmitting terminal, a transmitter, a transmitting apparatus, atransmitting side, a wireless power transmitting apparatus, a wirelesspower transmitter, a wireless charging apparatus, or the like forconvenience of description. Further, an apparatus for wirelesslyreceiving electric power from the wireless power sending apparatus maybe also called a wireless power receiving apparatus, a wireless powerreceiver, a receiving terminal, a receiving side, a receiving apparatus,a receiver terminal, or the like for convenience of description.

The wireless charging apparatus according to an embodiment may beprovided as a pad type, a support type, an access point (AP) type, asmall base station type, a stand type, a ceiling embedded type, a wallmount type, etc. and one transmitter may transmit electric power to aplurality of wireless power receiving apparatuses.

As an example, the wireless power transmitter may be typically used whenput on a desk or table and also used in a vehicle when developed for avehicle. The wireless power transmitter installed in the vehicle may beprovided as a support type to be conveniently and stably held andsupported.

A terminal according to an embodiment may be used for a small electronicdevice such as a mobile phone, a smart phone, a notebook computer (or alaptop computer), a digital broadcasting terminal, a personal digitalassistant (PDA), a portable multimedia player (PMP), a globalpositioning system (GPS), an MP3 player, an electric toothbrush, anelectronic tag, an illumination system, a remote controller, a fishingfloat, or the like, but not limited thereto. Alternatively, the terminalmay include any mobile device (hereinafter referred to as a “device”)provided with a wireless power receiving means according to anembodiment and capable of battery charging, and the terms “terminal” and“device” may both be used. According to another embodiment, the wirelesspower receiver may be mounted to a vehicle, an unmanned aircraft, an airdrone, etc.

According to an embodiment, the wireless power receiver may employ atleast one wireless power transmission manner, and may simultaneouslyreceive wireless power from two or more wireless power transmitters.Herein, the wireless power transmission manner may include at least oneamong an electromagnetic induction manner, an electromagnetic resonancemanner, and an RF wireless power transmission manner. In general, thewireless power transmitter and the wireless power receiver of thewireless power system may exchange a control signal or informationthrough in-band communication or Bluetooth low energy (BLE)communication. Herein, in-band communication and BLE communication maybe performed by a pulse width modulation (PWM) method, a frequencymodulation (FM) method, a phase modulation (PM) method, an amplitudemodulation (AM) method, an AM-PM method, etc. For example, the wirelesspower receiver generates a feedback signal by applying a predeterminedon/off switching pattern to an electric current induced through areceiving coil and thus transmits various control signals andinformation to the wireless power transmitter. The information receivedfrom the wireless power receiver may include various pieces ofinformation such as a level of received power. In this case, thewireless power transmitter may calculate a charging efficiency or apower transmission efficiency based on information about the level ofthe received power.

FIG. 1 is a block diagram for describing a wireless charging systemaccording to one embodiment.

Referring to FIG. 1 , the wireless charging system may generally includea wireless power transmitter 10 for wirelessly transmitting power, awireless power receiver 20 for receiving the transmitted power, and anelectronic device 30 to which the received power is supplied.

As an example, the wireless power transmitter 10 and the wireless powerreceiver 20 may perform in-band communication to exchange informationthrough the same frequency band as an operation frequency used inwirelessly transmitting power. Alternatively, the wireless powertransmitter 10 and the wireless power receiver 20 may performout-of-band communication to exchange information through a separatefrequency band different from the operation frequency used in wirelesslytransmitting the wireless power.

As an example, the information exchanged between the wireless powertransmitter 10 and the wireless power receiver 20 may include not onlytheir state information but also control information. Herein, the stateinformation and the control information exchanged in between thetransmitting/receiving terminals will become apparent throughdescriptions of the following embodiments.

In-band communication and out-of-band communication may providebidirectional communication, but the embodiment is not limited thereto.According to another embodiment, in-band communication and out-of-bandcommunication may provide unidirectional communication or half-duplexcommunication.

As an example, unidirectional communication may mean that the wirelesspower receiver 20 transmits information only to the wireless powertransmitter 10, but the embodiment is not limited thereto.Alternatively, the wireless power transmitter 10 may transmitinformation to the wireless power receiver 20.

The half-duplex communication allows bidirectional communication betweenthe wireless power receiver 20 and the wireless power transmitter 10,but allows only one of them to transmit information at a time.

According to an embodiment, the wireless power receiver 20 may obtainvarious pieces of state information of the electronic device 30. As anexample, the state information of the electronic device 30 may includeinformation about an amount of currently used power, information foridentifying running applications, information about usage of a centralprocessing unit (CPU), information about a battery charging state,information about battery output voltage/current, etc., but theembodiment is not limited thereto. Alternatively, the state informationmay include any information that may be obtained from the electronicdevice 30 and may be usable for wireless power control.

FIG. 2 is a state transition view for describing a wireless powertransmission process.

Referring to FIG. 2 , according to the wireless power transmissionprocess, the power transmission from the transmitter to the receiver isgenerally divided into a selection phase 210, a ping phase 220, anidentification and configuration phase 230, a negotiation phase 240, acalibration phase 250, a power transfer phase 260, and a renegotiationphase 270.

The selection phase 210 may be a transition phase—for example, includingreference numerals of S202, S204, S208, S210, S212—when a specific erroror a specific event is sensed while power transmission is started orpower transmission is maintained Herein, the specific error or thespecific event will become apparent through the following descriptions.Further, in the selection phase 210, the transmitter may monitor whetheran object is present on an interface surface. When the transmittersenses that an object is put on the interface surface, transition to theping phase 220 is possible. In the selection phase 210, the transmittertransmits an analog ping signal having a very short pulse and may sensewhether an object is present in an active area of the interface surfacebased on change in a current of the transfer coil or a primary coil.

When the object is sensed in the selection phase 210, the wireless powertransmitter may measure a quality factor of one end and/or the other endof a wireless power resonance circuit, e.g. the transfer coil and/or theresonance capacitor for transmitting the wireless power.

The wireless power transmitter may measure a peak frequency of thewireless power resonance circuit (e.g. the power transmission coiland/or the resonance capacitor).

Next, a quality coefficient and/or a peak frequency may be used in thenegotiation phase 240 to determine whether a foreign object is present.

When an object is sensed in the ping phase 220, the transmitter wakes upthe receiver and transmits a digital ping for identifying whether thesensed object is the wireless power receiver (S201). In the ping phase220, when the transmitter receives no response signal as a response tothe digital ping—for example, no signal strength packet—from thereceiver, transition to the selection phase 210 is possible. Further,when the transmitter receives a signal—i.e. a charging completionpacket—informing that the power transmission has been completed,transition from the ping phase 220 to the selection phase 210 may bepossible (S202).

When the ping phase 220 is completed, the transmitter identifies thereceiver and enters the identification and configuration phase 230 forcollecting information about the configuration and state of the receiver(S203).

When an unexpected packet is received, an expected packet goes beyond apredetermined time limit (i.e. times out), there is a packet transfererror, or no power transmission contract is set in the identificationand configuration phase 230, the transmitter may return to the selectionphase 210 (S204).

The transmitter may determine whether there is a need for entering thenegotiation phase 240 based on a negotiation field value of aconfiguration packet received in the identification and configurationphase 230.

As a result of determination, when the negotiation is needed, thetransmitter may enter the negotiation phase 240 (S205). In thenegotiation phase 240, the transmitter may perform a predeterminedforeign object detection (FOD) process.

On the other hand, as a result of determination, when the negotiation isnot needed, the transmitter may directly enter the power transmissionphase 260 (S206).

In the negotiation phase 240, the transmitter may receive an FOD statepacket including a reference quality factor value, or may receive an FODstate packet including a reference peak frequency value, or may receivea state packet including the reference quality factor value and thereference peak frequency value. In this case, the transmitter maydetermine a threshold quality factor value for detecting a foreignobject (FO) based on the reference quality factor value. The transmittermay determine a threshold peak frequency value for detecting an FO basedon the reference peak frequency value.

Using the threshold quality factor value for detecting the determined FOand the currently measured quality factor value—for example, the qualityfactor value measured before the ping phase—, the transmitter may detectwhether an FO is present in a charging region and control the powertransmission in accordance with FO detection results. For example, whenthe FO is detected, the power transmission may be stopped, but theembodiment is not limited thereto.

Using the threshold peak frequency value for detecting the determined FOand the current measured peak frequency value—for example, the peakfrequency value measured before the ping phase—, the transmitter maydetect whether an FO is present in the charging region and control thepower transmission in accordance with FO detection results. As anexample, when the FO is detected, the power transmission may be stopped,but the embodiment is not limited thereto.

When the FO is detected, the transmitter may return to the selectionphase 210 (S208). On the other hand, when the FO is not detected, thetransmitter may enter the power transmission phase 260 via thecalibration phase 250 (S207 and S209). In detail, when the FO is notdetected, the transmitter may receive the level of the electric powerreceived in the receiving terminal, and may compare the level of theelectric power transmitted from the transmitting terminal in thecalibration phase 250 to measure power loss in the receiving terminaland the transmitting terminal. That is, the transmitter may predict thepower loss based on difference between the power transmitted from thetransmitting terminal and the power received in the receiving terminalduring the calibration phase 250. The transmitter according to oneembodiment may calibrate a power loss threshold value for detecting theFOD by reflecting the predicted power loss. That is, in the calibrationphase, since there is no FO, it is determined that the power loss due toa coupling state of the receiver and a friendly metal content of thereceiver, and it may be determined that a foreign object is present whenadditional power loss other than a predetermined power loss occurs.

When an unexpected packet is received, an expected packet goes beyond apredetermined time limit (i.e. times out), preset power transmissioncontract is violated, or charging is completed, the transmitter in thepower transmission phase 260 may return to the selection phase 210(S210).

Further, in the power transmission phase 260, when there is a need forreconfiguring the power transmission contract in accordance with changesin the state of the transmitter, the transmitter may enter therenegotiation phase 270 (S211). In this case, the renegotiation isnormally completed, and the transmitter may return to the powertransmission phase 260 (S213).

The power transmission contract may be set based on the state andcharacteristic information of the transmitter and the receiver. Forexample, the state information of the transmitter may includeinformation about the maximum transmittable power, information about themaximum supportable number of the receivers, etc., and the stateinformation of the receiver may include information about requiredelectric power.

When the renegotiation is not normally completed, the transmitter maystop transmitting the electric power to the corresponding the receiverand return to the selection phase 210 (S212).

FIG. 3 is a block diagram describing a structure of a wireless powertransmitter according to one embodiment.

Referring to FIG. 3 , a wireless power transmitter 300 includes a powersupply 360, a DC-DC converter 310, an inverter 320, a resonance circuit330, a sensor 350, a communication unit 340, an alarm unit 370, and acontroller 380.

The resonance circuit 330 includes a resonance capacitor 331 and aninductor (or transmission coil) 332. The communication unit 340 includesat least one of a demodulator 341 and a modulator 342.

The power supply 360 may receive DC power from an external power supplyterminal or a battery and transmit it to the DC-DC converter 310. Here,the battery may be configured to be installed inside the wireless powertransmitter 300 so as to be chargeable, but it is merely an example, andmay be connected to the power supply 360 of the wireless powertransmitter 300 via a predetermined cable in a form of an auxiliarybattery or an external battery.

The DC-DC converter 310 may convert a level of DC power input from thepower supply 360 into DC power having a specific level according to acontrol of the controller 380. As an example, the DC-DC converter 310may be configured as a variable voltage generator capable of controllinga level of voltage, but the embodiment is not limited thereto.

The inverter 320 may convert the converted DC power into AC power.

The inverter 320 may convert a DC power signal input through control ofa plurality of switches included therein into an AC power signal andoutput the AC power signal.

As an example, the inverter 320 may include a full-bridge circuit, butthe embodiment is not limited thereto, and may include a half-bridge.

As another example, the inverter 320 may be configured to include both ahalf-bridge circuit and a full-bridge circuit, and in this case, thecontroller 380 may dynamically determine whether to operate the inverter320 in a half-bridge or a full-bridge to control.

The wireless power transmitter according to one embodiment mayadaptively control a bridge mode of the inverter 320 according to alevel of power required by the wireless power receiver.

Here, the bridge mode includes a half-bridge mode and a full-bridgemode. As an example, when the wireless power receiver requires a lowpower of 5 W, the controller 380 may control the inverter 320 so as tooperate in the half-bridge mode.

On the other hand, when the wireless power receiver requires 15 W ofpower, the controller 380 may control to operate in the full-bridgemode. As another example, the wireless power transmitter may adaptivelydetermine the bridge mode according to the sensed temperature and drivethe inverter 320 according to the determined bridge mode.

As an example, when a temperature of a wireless power transmissiondevice exceeds a predetermined reference value during transmission ofwireless power through the half-bridge mode, the controller 380 maycontrol such that the half-bridge mode is disabled and the full-bridgemode is enabled. That is, the wireless power transmission deviceincreases a voltage through a full-bridge circuit and reduces a level ofcurrent flowing in the resonance circuit 330 for the same level of powertransmission, and thus the internal temperature of the wireless powertransmitter may be controlled so as to be maintained below thepredetermined reference value.

Generally, an amount of heat generated in an electronic componentmounted on an electronic device may be more sensitive to the level ofcurrent than the level of voltage applied to the electronic component.

In addition, the inverter 320 may change a level of AC power as well asconvert DC power to AC power.

As an example, the inverter 320 may adjust a frequency of a referencealternating current signal used for generating AC power according tocontrol of the controller 380 to adjust the level of AC power. To thisend, the inverter 320 may include a frequency oscillator that generatesa reference AC signal having a specific frequency, but it is merely oneexample, and in another example, the frequency oscillator may beconfigured separately from the inverter 320 and mounted on one side ofthe wireless power transmitter 300.

As another example, the wireless power transmitter 300 may furtherinclude a gate driver (not shown) for controlling a switch provided inthe inverter 320. In this case, the gate driver may receive at least onepulse width modulation signal from the controller 380, and may controlthe switch of the inverter 320 according to the received pulse widthmodulation signal. The controller 380 may control the duty cycle of thepulse width modulation signal—i.e. a duty rate—and a phase to control alevel of output power of the inverter 320. The controller 380 mayadaptively control the duty cycle and phase of the pulse widthmodulation signal based on a feedback signal received from the wirelesspower receiving apparatus.

The sensor 350 may measure the voltage/current of the DC-converted powerto provide them to the controller 380. In addition, the sensor 350 maymeasure an internal temperature of the wireless power transmitter 300 oran inside of a charging interface (surface) in order to determinewhether overheating occurs, and provide a measurement result to thecontroller 380. As an example, the controller 380 adaptively cut off thepower supplied from the power supply 380 based on the voltage/currentvalue or the internal temperature value measured by the sensor 350. Tothis end, a predetermined power cut-off circuit may be further providedat one side of the DC-DC converter 310 to cut off the power suppliedfrom the power supply 360.

In addition, the sensor 350 may include various sensing elements forsensing a quality factor value, a frequency value, an equivalent seriesresistance value, and the like. The sensor 350 may provide the sensedquality factor, frequency value, equivalent series resistance, etc. tothe controller 380. A sensing method of the sensor 350 followsdescriptions of FIGS. 6 to 18 .

The controller 380 may detect a foreign object using FOD stateinformation including at least one of the sensed quality factor value,frequency value, equivalent series resistance value, and the like, andthe received reference quality factor value and the reference frequencyvalue. A foreign object detection method of the controller 380 followsdescriptions of FIGS. 6 to 18 .

A modulator 342 modulates the control signal generated by the controller380 and transmits it to the resonance circuit 330. Herein, a method ofmodulating the control signal may include a frequency shift keying (FSK)modulation method, a Manchester coding modulation method, a phase shiftkeying (PSK) modulation method, a pulse width modulation (PWM) method, adifferential bi-phase modulation method, etc. without limitations.

When sensing a signal received through the transmission coil, thedemodulator 341 demodulates the sensed signal and transmits it to thecontroller 380. As an example, the demodulated signal may include asignal strength indicator, an error calibration (EC) indicator forcontrolling electric power during the wireless power transfer, anend-of-charge (EOC) indicator, an overvoltage/overcurrent/overheatindicator, etc. without limitations, and may include various pieces ofstatus information for identifying the state of the wireless powerreceiver. As another example, the demodulated signal may include FODstate information including a value of at least one of a referencequality factor value and a reference frequency value.

As an example, the wireless power transmitter 300 may obtain the signalstrength indicator via in-band communication that uses the samefrequency used for wireless power transmission to communicate with thewireless power receiver.

In the foregoing description with FIG. 3 , the wireless powertransmitter 300 and the wireless power receiver perform the In-bandcommunication, but this is merely an embodiment. Alternatively, they mayperform a near field interactive communication through a frequency banddifferent from the frequency band used in transmitting the wirelesspower signal. For example, the near field interactive communication maybe one among low power Bluetooth communication, RFID communication, UWBcommunication, ZigBee communication, etc.

FIG. 4 is a block diagram for describing a structure of a wireless powerreceiver interworking with the wireless power transmitter according toFIG. 3 .

Referring to FIG. 4 , a wireless power receiver 400 may include areceiving coil 410, a rectifier 420, a DC/DC converter 430, a load 440,a sensor 450, a communication unit 460, and a main controller 470.Herein, the communication unit 460 may include at least one of ademodulator 461 and a modulator 462.

The wireless power receiver 400 shown in the example of FIG. 4 exchangesinformation with the wireless power transmitter through the In-bandcommunication, but this is merely an embodiment. According to anotherembodiment the communication unit 460 may perform the near fieldinteractive communication through a frequency band different from thefrequency band used in transmitting the wireless power signal.

The AC power received through the receiving coil 410 may be transferredto the rectifier 420. The rectifier 420 may convert the AC power into DCpower and transmission it to the DC/DC converter 430. The DC/DCconverter 430 may convert the level of the DC power output from therectifier into a specific level required by the load 440 and thentransmission it to the load 440. Further, the receiving coil 410 mayinclude a plurality of receiving coil (not shown)—i.e., the first to nthreceiving coils. According to one embodiment, frequencies of the ACpower transferred to the receiving coils (not shown) may be differentfrom each other. According to another embodiment, a predeterminedfrequency controller having a function of adjusting the receiving coilsto have different LC resonance characteristics may be used to set theresonance frequencies of the receiving coils differently.

The sensor 450 may measure the level of the DC power output from therectifier 420, and provides it to the main controller 470. Further, thesensor 450 may measure the intensity of the current applied to thereceiving coil 410 in accordance with reception of the wireless power,and transmits the measured results to the main controller 470. Further,the sensor 450 may measure the internal temperature of the wirelesspower receiver 700, and provides the measured temperature value to themain controller 470.

For example, the main controller 470 may compare the measured level ofthe DC power output from the rectifier with a predetermined referencevalue, and determine whether an overvoltage is generated or not. As aresult of determination, when the overvoltage is generated, the maincontroller 470 may make a predetermined packet for informing theovervoltage, and transmits the packet to the modulator 462. Herein, asignal modulated by the modulator 462 may be transmitted to the wirelesspower transmitter through the receiving coil 410 or a separate coil (notshown). Further, when the level of the DC power output from therectifier is equal to or higher than a predetermined reference value,the main controller 470 may determine that a sensing signal is received,and control the signal strength indicator corresponding to the sensingsignal may be transmitted to the wireless power transmitter through themodulator 462 when the sensing signal is received. Alternatively, thedemodulator 461 may modulate a DC power signal output from the rectifier420 or an AC power signal between the receiving coil 410 and therectifier 420 and determine whether a sensing signal is received,thereby providing a determination result to the main controller 470. Inthis case, the main controller 470 may perform control so that thesignal strength indicator corresponding to the sensing signal may betransmitted via the modulator 462.

In addition, the main controller 470 may control so that the FOD statepacket including at least one of the previously stored reference qualityfactor and the reference frequency value may be transmitted to thewireless power transmitter via the modulator 462.

FIG. 5 is a view for describing a wireless charging method on a wirelesscharging system according to one embodiment.

Referring to FIG. 5 , a wireless power transmitter 610 may transmit ananalog ping to a wireless power receiver 620 in a selection phase(S601).

The wireless power transmitter 610 may measure a quality factor valuebefore a ping phase (S602). As an example, the wireless powertransmitter 610 may measure the quality factor value in the selectionphase (S602).

In addition, the wireless power transmitter 610 may measure a peakfrequency value before the ping phase (S603). As an example, thewireless power transmitter 610 may measure the peak frequency value inthe selection phase (S602). As another example, the wireless powertransmitter 610 may determine an inductance value by measuring the peakfrequency of the transmission coil in the selection phase. Morespecifically, referring to Equation 1, the frequency value f may bedetermined using a fixed capacitance value C and a measured inductancevalue.

$\begin{matrix}{f = \frac{1}{2\pi\sqrt{LC}}} & ( {{Equation}1} )\end{matrix}$

The wireless power transmitter 610 may transit from the selection phaseto the ping phase when an object is sensed. The wireless powertransmitter 610 may activate the wireless power receiver 620, and maytransmit a digital ping to identify whether a receiver is the wirelesspower receiver 620 (S604). The wireless power receiver 620 may transmita signal strength packet in response to the digital ping (S603).

When the ping phase is completed, in the identifying and configuringphase, the wireless power receiver 620 may transmit an identificationpacket to inform the identification information and a configurationpacket to inform the configuration information (S606 to S607). Thewireless power transmitter 610 and the wireless power receiver 620 maytransition to a negotiation phase when a negotiation field value of theconfiguration packet is a value indicating to perform the negotiationphase.

In the negotiation phase, the wireless power receiver 620 may transmit aFOD status packet for FO detection (S606). The FOD state packet mayinclude one or more of a reference quality factor value and a referencefrequency value.

The wireless power transmitter 610 may perform first foreign objectdetection (S609). The first foreign object detection may detect aforeign object by using a measured quality factor value, a measuredfrequency value, and information of a received FOD status packet. Thefirst foreign object detection is according to descriptions of awireless charging method of FIGS. 7 to 12 .

The wireless power transmitter 610 may transmit an ACK to the wirelesspower receiver 620 in response to the FOD status packet (S610) when itis determined to perform wireless charging after performing the firstforeign object detection. Conversely, the wireless power transmitter 610may transmit an NAK to the wireless power receiver 620 in response tothe FOD status packet when it is determined to stop wireless chargingafter performing the first foreign object detection.

The wireless power receiver 620 may transmit a general request packetrequesting a power transmitter capability packet for a powertransmission contract (S611). The wireless power transmitter 620 maytransmit the power transmitter capability packet in response to thegeneral request packet (S612). In this case, a guaranteed power of thepower transmitter capability packet may be a first guaranteed powervalue.

A potential power value may be a maximum transmission power value thatmay be transmitted by a wireless power transmitter regardless of powerlimitation due to surrounding requirements. As an example, the firstguaranteed power value may be a value close to a potential power valuethat is not subject to power limitations due to a number of wirelesspower transmitters or a number of wireless power receivers based on asupply power provided from a power supply of the wireless powertransmitter. As another example, the first guaranteed power value may bea maximum transmission power value that may be transmitted by thewireless power transmitter under conditions (environmental conditions)such as power limitation due to the number of wireless powertransmitters or the number of wireless power receivers. Theenvironmental conditions may refer to a temperature of the transmitter,a capacity of the transmitter's power source, the presence of foreignobject, or influence of friendly metal. The wireless power receiver 620may transmit a specific request packet to propose the guaranteed powervalue of the power transmission contract based on the first guaranteedpower value of the power transmitter capability packet (S613). It shouldbe noted that the first guaranteed power of the power transmittercapability packet and the guaranteed power of the power transmissioncontract may be distinguished. For example, the wireless power receiver620 may request a guaranteed power value of the power transmissioncontract with a value equal to or less than the first guaranteed powervalue of the power transmitter capability packet. For convenience ofdescription, the wireless power receiver 620 requests the guaranteedpower value of the power transmission contract as the same value as thefirst guaranteed power value of the power transmitter capability packet.The wireless power transmitter 610 may transmit an ACK packet inresponse to a specific request packet for requesting a guaranteed powervalue of the power transmission contract (S614). That is, the wirelesspower transmitter 610 is in a case in which the guaranteed power valueof the power transmission contract proposed by the wireless powerreceiver is accepted. That is, the power transmission contract may becompleted with the first guaranteed power value. Thereafter, when thepower transmission contract is completed, the wireless power receiver620 may transmit a specific request packet for ending the negotiationphase (S615). The wireless power transmitter 610 may transmit an ACKpacket in response to the specific request packet for ending thenegotiation phase (S616). That is, the wireless power transmitter 610may transmit an ACK packet upon acceptance of the end of the negotiationphase.

In the calibration phase, the wireless power receiver 620 may transmitthe received power packet to the wireless power transmitter 610 (S617).In this case, the received power packet may be a 24-bit received powerpacket. The wireless power transmitter 610 may transmit an ACK packet inresponse to the received power packet in order to perform wirelesscharging (S618).

The wireless power transmitter 610 may determine whether to perform thecalibration (S619). The determination of whether to perform thecalibration is a case in which performing the calibration phase in FIGS.6 to 13 is entered. As an example, when it is determined to perform thecalibration, in performing the calibration, the wireless powertransmitter 610 may predict power loss by using the received power valueof the wireless power receiver 610 of the received power packet receivedat S617 and the measured transmission power value. In addition, inperforming the calibration, the wireless power transmitter 610 maycalibrate a threshold value of power loss used in the second foreignobject detection (S623) performed in the power transfer phase by using apredicted power loss value. In addition, in performing the calibration,the wireless power transmitter 610 may increase strength of thetransmission power by using the predicted power loss value. The wirelesspower transmitter may not perform the calibration according to thepresence or absence of foreign object (when it is present).

When the calibration phase is completed, the power transfer phase may beperformed with the first guaranteed power. The wireless power receiver620 may transmit one or more control error packets in order to controlthe current of the transmission coil of the wireless power transmitter610 (S620). The wireless power transmitter 610 may control thetransmission power by controlling the current of the transmission coilbased on the control error packet transmitted from the wireless powerreceiver 620. The wireless power receiver 620 may transmit the receivedpower packet periodically or arbitrarily (S621).

The wireless power transmitter 610 may perform the second foreign objectdetection (S622). For example, the wireless power transmitter 610 maydetermine power loss using the received power value of the receivedpower packet and the measured transmission power value, and may detectthe presence or absence of a foreign object according to a power lossvalue. That is, when the power loss value exceeds a predeterminedthreshold power loss value, it may be determined that the foreign objectis present. In this case, the wireless power transmitter 610 maytransmit a NAK packet to the wireless power receiver 620 in response tothe received power packet to stop charging (S623). Thereafter, thewireless power transmitter 610 may stop wireless charging (S624). Asanother example, the wireless power transmitter 610 may detect thepresence or absence of a foreign object by using the measured internaltemperature value regardless of whether or not the received power packetis received. That is, when the internal temperature value exceeds apredetermined threshold temperature value, it may be determined that aforeign object is present. In this case, the wireless power transmitter610 may stop wireless charging.

Therefore, the wireless charging system according to the embodiment mayprovide a wireless charging method and an apparatus and system therefor.In addition, the wireless charging system according to the embodimentmay determine a foreign object accurately. Further, the wirelesscharging system according to the embodiment may accurately determine aforeign object to prevent a heat generation phenomenon, a decrease incharging efficiency, and a loss of power consumption.

FIG. 6 is a view for describing a wireless charging method in a wirelesspower transmitter according to an embodiment, FIG. 7 is a view fordescribing a foreign object detection method according to a qualityfactor value.

Referring to FIG. 6 , the wireless charging method in the wireless powertransmitter may include measuring a quality factor value before a pingphase (S701). For example, the wireless power transmitter may measurethe quality factor value using a sensor in a selection phase.

The wireless charging method in the wireless power transmitter mayinclude receiving a FOD status packet including a reference qualityfactor value (S702). As an example, the wireless power transmitter mayreceive an FOD status packet using a communication unit in a negotiationphase. The reference quality factor value is a quality factor valuestored in the wireless power receiver, and may be a quality factor valuemeasured in a specific coil unit. Here, the specific coil unit is a coilunit used as a reference for comparing the quality factor value, and thewireless power transmitter should to calibrate the quality factor valueto be similar to the value measured in the reference coil unit accordingto the characteristics of the coil unit. Alternatively, on the contrary,the reference quality factor value measured in the reference coil unitmay be calibrated to the value measured in the wireless powertransmitter.

However, it is very difficult to calibrate (convert) the referencequality factor value according to the characteristics of the wirelesspower transmitter or to calibrate (convert) the measured value accordingto the specific coil unit. This is because a quality factor is anintrinsic characteristic value of the coil unit, and energy storage andloss are shown differently depending on the characteristic. Therefore,detecting a foreign object using the quality factor value may beerroneous. For example, even when only the wireless power receiver isdisposed in a charging region, it may be determined as a foreign objectby a measurement error and/or a calibration error. A terminal equippedwith a wireless power receiver such as a mobile phone has a plurality ofcomponents other than the wireless power receiver, and thus thereference quality factor value may be very low. When a measured qualityfactor value or a calibrated quality factor value has a differencegreater than the reference quality factor value (e.g., more than atolerance), a false alarm may be generated as a foreign object.Therefore, even though the foreign object is determined in detecting afirst foreign object, it is possible to determine whether or not theforeign object is present by an additional operation withoutinterrupting the power transmission.

The wireless charging method in the wireless power transmitter mayinclude determining a threshold quality factor value (S703). Morespecifically, the wireless power transmitter may calculate the thresholdquality factor value using the received reference quality factor value.As an example, the wireless power transmitter may determine a value lessthan 10% in the reference quality factor value as a threshold qualityfactor value. 10% is a tolerance of the reference quality factor value,and when a foreign object is present, the foreign object may be detectedby using that a measured quality factor value which is at least thetolerance or more becomes smaller than the reference quality factorvalue.

The wireless charging method in the wireless power transmitter mayinclude determining an acceptable quality factor value (S704). Morespecifically, the wireless power transmitter may calculate theacceptable quality factor value using the determined threshold qualityfactor value. As an example, as shown in FIG. 7 , the wireless powertransmitter may determine a value reduced by more than 0% and 20% orless in a threshold quality factor value Qth as an acceptable qualityfactor value Qp. More specifically, the wireless power transmitter maydetermine a value reduced by 20% in the threshold quality factor valueas the acceptable quality factor value.

The wireless charging method in the wireless power transmitter mayinclude determining whether the measured quality factor value is greaterthan or equal to the determined acceptable quality factor value (S705).

When the quality factor value is equal to or greater than the acceptablequality factor value, the wireless power transmitter may determine toperform wireless charging (S706). When the quality factor value is lessthan the acceptable quality factor value, the wireless power transmittermay determine to stop wireless charging (S714). For example, as shown inFIG. 8 , when a frequency of the transmission power is a firstfrequency, the quality factor measured in the wireless power transmittermay be a first quality factor value Q1, a second quality factor valueQ2, and a third quality factor value Q3. When measured as the firstquality factor value Q1, since there is a very high probability that aforeign object is not present between the wireless power transmitter andthe wireless power receiver, it is possible to determine that theforeign object is not present. When measured as the third quality factorvalue Q3, since the third quality factor value Q3 is much lower than thethreshold quality factor value Qth, and there is a very high probabilitythat a foreign object is not present between the wireless powertransmitter and the wireless power receiver, it is possible to determinethat the foreign object is not present. When measured as the secondquality factor value Q2, since the second quality factor value Q2 isbetween the threshold quality factor value Qth and the acceptablequality factor value Qp, it may be misrecognized as a foreign object ispresent between the wireless power transmitter and the wireless powerreceiver. In order to prevent this, the wireless power transmitter mayperform wireless charging when the measured quality factor value isgreater than or equal to the acceptable quality factor value.Thereafter, the wireless power transmitter may determine more accuratelywhether a foreign object is present or not by performing detection of asecond foreign object in the power transfer phase of S711. Therefore,the wireless power transmitter may determine to perform wirelesscharging when the quality factor value is greater than or equal to theacceptable quality factor value. Accordingly, one embodiment maydetermine a foreign object accurately. In addition, one embodiment mayaccurately determine the foreign object to prevent a heat generationphenomenon, a decrease phenomenon in charging efficiency, and a loss ofpower consumption. Further, one embodiment may solve a problem in whichwireless charging is not performed by erroneously recognizing that aforeign object is present in the related art.

When the wireless power transmitter determines to perform wirelesscharging, the ACK packet may be transmitted to the wireless powerreceiver in response to receiving the FOD status packet (S707).

The wireless charging method in the wireless power transmitter mayinclude a step of determining whether the wireless power transmitter hasa quality factor value greater than or equal to a threshold qualityfactor value (S708). More specifically, the wireless power transmittermay determine whether the quality factor value is greater than or equalto the threshold quality factor value in order to determine whether toperform calibration after transition to the calibration phase afterdetermining to perform wireless charging in the negotiation phase.

The wireless charging method in the wireless power transmitter mayinclude a step of performing the calibration after transition to thecalibration phase (S709) when the quality factor value is greater thanor equal to the threshold quality factor value. As an example, inperforming the calibration, the wireless power transmitter may predictpower loss by using the received power value of the wireless powerreceiver of the received power packet and the measured transmissionpower value. In addition, in performing the calibration the wirelesspower transmitter may increase strength of the transmission power byusing the predicted power loss value.

In the wireless charging method in the wireless power transmitter, whenthe quality factor value of the wireless power transmitter is less thanthe threshold quality factor value, the wireless power transmitter maytransition to the power transfer phase (S710) without the calibrationphase.

The wireless charging method in the wireless power transmitter mayinclude performing detection of the second foreign object (S711) whenreceiving the received power packet after transition to the powertransfer phase. The wireless power transmitter may stop wirelesscharging when it is determined that the foreign object has been detectedby performing detection of the second foreign object (S712, S713). Inaddition, the wireless power transmitter may maintain the power transferphase when it is determined that the foreign object is not detected byperforming detection of the second foreign object, and may performdetection of the second foreign object again when the received powerpacket is received (S712, S711). As an example, in the power transferphase, the wireless power transmitter may determine power loss using thereceived power value of the received power packet and the measuredtransmission power value, and may detect the presence or absence of aforeign object according to the power loss value. When the power lossvalue exceeds a predetermined threshold power loss value, the wirelesspower transmitter may determine that a foreign object is present. Inthis case, the wireless power transmitter may transmit an NAK packet tothe wireless power receiver in response to the received power packet inorder to stop charging. Thereafter, the wireless power transmitter maystop wireless charging. As another example, the wireless powertransmitter may detect the presence or absence of a foreign object usingthe measured internal temperature value regardless of whether or not thereceived power packet is received. That is, when the internaltemperature value exceeds a predetermined threshold temperature value,it is possible to determine that a foreign object is present. In thiscase, the wireless power transmitter may stop wireless charging.Therefore, in one embodiment, even though detection of foreign object issuspected in the negotiation phase, the wireless charging is performedwithout stopping the wireless charging, and then the foreign object isdetected again in the power transfer phase to accurately determinewhether the foreign object is present.

When the wireless power transmitter determines to stop wireless chargingin S714, the wireless power transmitter may transmit an NAK packet tothe wireless power receiver in response to receiving the FOD statuspacket (S715). Thereafter, the wireless power transmitter may stopwireless charging (S713).

FIG. 8 is a view for describing a wireless charging method in a wirelesspower transmitter according to another embodiment, and FIG. 9 is a viewfor describing a foreign object detection method according to a peakfrequency value.

Referring to FIG. 8 , the wireless charging method in the wireless powertransmitter may include measuring a peak frequency value (S901) before aping phase. As an example, the wireless power transmitter may use asensor to measure the peak frequency value of transmission power in aselection phase.

The wireless charging method in the wireless power transmitter mayinclude receiving an FOD status packet including a reference peakfrequency value (S902). As an example, the wireless power transmittermay receive the FOD status packet using a communication unit in anegotiation phase. The reference peak frequency value may be a peakfrequency value of a received power stored in the wireless powerreceiver.

The wireless charging method in the wireless power transmitter mayinclude determining a threshold peak frequency value (S903). Morespecifically, the wireless power transmitter may calculate the thresholdpeak frequency value using the received reference peak frequency value.As an example, the wireless power transmitter may determine a valueincreased by 10% in the reference peak frequency value as a thresholdpeak frequency value. 10% is a tolerance of the reference peak frequencyvalue, and when a foreign object is present, the foreign object may bedetected by using that a measured peak frequency value which is at leastthe tolerance or more becomes larger than the reference peak frequencyvalue.

The wireless charging method in the wireless power transmitter mayinclude determining the acceptable peak frequency value. Morespecifically, the wireless power transmitter may calculate theacceptable peak frequency value using the determined threshold peakfrequency value. As an example, as shown in FIG. 9 , the wireless powertransmitter may determine a value reduced by more than 0% and 20% orless in a threshold peak frequency value fth as an acceptable peakfrequency value fp. More specifically, the wireless power transmittermay determine a value reduced by 20% in the threshold peak frequencyvalue as the acceptable peak frequency value.

The wireless charging method in the wireless power transmitter mayinclude determining whether the measured peak frequency value is lessthan or equal to the determined acceptable peak frequency value.

When the peak frequency value is less than or equal to the acceptablepeak frequency value, the wireless power transmitter may determine toperform wireless charging (S906). When the peak frequency value exceedsthe acceptable peak frequency value, the wireless power transmitter maydetermine to stop wireless charging (S914). For example, as shown inFIG. 9 , the peak frequency measured in the wireless power transmittermay be a first peak frequency value f1, a second peak frequency valuef2, and a third peak frequency value f3. When measured as the first peakfrequency value f1, since there is a very high probability that aforeign object is not present between the wireless power transmitter andthe wireless power receiver, it is possible to determine that theforeign object is not present. When measured as the third peak frequencyvalue f3, since the third peak frequency value f3 is very high than thethreshold peak frequency value fth, and there is a very high probabilitythat the foreign object is present between the wireless powertransmitter and the wireless power receiver, it is possible to determinethat the foreign object is present. When measured as the second peakfrequency value f2, since the second peak frequency value f2 is betweenthe threshold peak frequency value Qth and the acceptable peak frequencyvalue fp, it may be misrecognized that the foreign object is presentbetween the wireless power transmitter and the wireless power receiver.In order to prevent this, the wireless power transmitter may performwireless charging when the measured peak frequency value is greater thanor equal to the acceptable peak frequency value. Thereafter, thewireless power transmitter may more accurately determine whether aforeign object is present by performing second foreign object detectionin the power transfer phase of S911. Therefore, the wireless powertransmitter may determine to perform wireless charging when the peakfrequency value is less than or equal to the acceptable peak frequencyvalue. Accordingly, still another embodiment may accurately determinethe foreign object. In addition, still another embodiment may accuratelydetermine the foreign object to prevent a heat generation phenomenon, areduction phenomenon in charging efficiency, and a loss of powerconsumption. In addition, still another embodiment may solve a problemthat the wireless charging is not performed by erroneously recognizingthat a foreign object is present in the related art.

When it is determined to perform wireless charging, the wireless powertransmitter may transmit an ACK packet to the wireless power receiver inresponse to receiving the FOD status packet (S907).

The wireless charging method in the wireless power transmitter mayinclude the determining of whether the peak frequency value is less thanor equal to the threshold peak frequency value (S908). Morespecifically, the wireless power transmitter may determine whether thepeak frequency is less than or equal to the threshold peak frequencyvalue in order to determine whether to perform calibration aftertransition to the calibration phase after determining to performwireless charging in the negotiation phase.

The wireless charging method in the wireless power transmitter mayinclude performing calibration after transition to a calibration phasewhen the peak frequency value is less than or equal to the thresholdpeak frequency value (S909). As an example, in performing thecalibration, the wireless power transmitter may predict power loss byusing the received power value of the wireless power receiver of thereceived power packet and the measured transmission power value. Inaddition, in performing the calibration, the wireless power transmittermay increase strength of the transmission power by using the predictedpower loss value.

In the wireless charging method in a wireless power transmitter, whenthe wireless power transmitter exceeds the threshold peak frequencyvalue, the wireless power transmitter may transition to power transferphase (S910) without a calibration phase.

The wireless charging method in the wireless power transmitter mayinclude performing the second foreign object detection (S911) whenreceiving the received power packet after transition to the powertransfer phase. The wireless power transmitter may stop wirelesscharging when it is determined that the foreign object has been detectedby performing the second foreign object detection (S912, S913). Inaddition, the wireless power transmitter may maintain the power transferphase when it is determined that the foreign object is not detected byperforming the second foreign object detection, and may perform thesecond foreign object detection again when the received power packet isreceived (S912, S911). As an example, in the power transfer phase, thewireless power transmitter may determine power loss using the receivedpower value of the received power packet and the measured transmissionpower value, and may detect the presence or absence of a foreign objectaccording to a power loss value. When the power loss value exceeds apredetermined threshold power loss value, the wireless power transmittermay determine that a foreign object is present. In this case, thewireless power transmitter may transmit an NAK packet to the wirelesspower receiver in response to the received power packet in order to stopcharging. Thereafter, the wireless power transmitter may stop wirelesscharging. As another example, the wireless power transmitter may detectthe presence or absence of a foreign object using a measured internaltemperature value regardless of whether or not the received power packetis received. That is, when the internal temperature value exceeds apredetermined threshold temperature value, it is possible to determinethat a foreign object is present. In this case, the wireless powertransmitter may stop wireless charging. Therefore, in anotherembodiment, even though foreign object detection is suspected in thenegotiation phase, the wireless charging is performed without stoppingthe wireless charging, and then the foreign object is detected again inthe power transfer phase to accurately determine whether the foreignobject is present.

When the wireless power transmitter determines to stop wireless chargingin S914, the wireless power transmitter may transmit the NAK packet tothe wireless power receiver in response to receiving the FOD statuspacket (S915). Thereafter, the wireless power transmitter may stopwireless charging (S913).

FIG. 10 is a view for describing a wireless charging method in awireless power transmitter according to still another embodiment, andFIG. 11 is a view for describing a foreign object detection methodaccording to an equivalent series resistance value.

Referring to FIG. 10 , the wireless charging method in the wirelesspower transmitter may include measuring the equivalent series resistancevalue before a ping phase (S1101). As an example, the wireless powertransmitter may measure the equivalent series resistance value using asensor in a selection phase.

The wireless charging method in the wireless power transmitter mayinclude receiving an FOD status packet including a reference qualityfactor value and a reference peak frequency value (S1102). As anexample, the wireless power transmitter may receive the FOD statuspacket using a communication unit in a negotiation phase. The referencequality factor value and the reference peak frequency value may be aquality factor value and a peak frequency value stored in the wirelesspower receiver.

The wireless charging method in the wireless power transmitter mayinclude determining a threshold equivalent series resistance value(S1103). More specifically, the wireless power transmitter may determinethe reference equivalent series resistance value using the receivedreference quality factor value and the reference peak frequency value.More specifically, a reference equivalent series resistance value ESRrmay be calculated by substituting a reference peak frequency value fr, areference quality factor value Qr, and a reference peak frequency valueLr into Equation 2. Referring to Equation 3, the reference peakfrequency value Lr may be determined using a fixed capacitance value Crof the wireless power receiver and a received reference peak frequencyvalue fr.

$\begin{matrix}{{ESRr} = \frac{2{\pi{frLr}}}{Qr}} & ( {{Equation}2} )\end{matrix}$ $\begin{matrix}{{fr} = \frac{1}{2\pi\sqrt{LrCr}}} & ( {{Equation}3} )\end{matrix}$

As an example, the wireless power transmitter may determine a valueincreased by 10% in the reference equivalent series resistance value asa threshold equivalent series resistance value ESRth. As anotherexample, the wireless power transmitter may determine a maximumreference equivalent series resistance value ESRmax as the thresholdequivalent series resistance value ESRth. 10% is a tolerance of thereference equivalent series resistance value, and when a foreign objectis present, the foreign object may be detected by using that a measuredequivalent series resistance value which is at least the tolerance ormore becomes greater than the reference equivalent series resistancevalue.

The wireless charging method in the wireless power transmitter mayinclude determining an acceptable equivalent series resistance value(S1104). More specifically, the wireless power transmitter may calculatethe acceptable equivalent series resistance value using the determinedthreshold equivalent series resistance value. As an example, as shown inFIG. 11 , the wireless power transmitter may determine a value increasedby more than 0% and 20% or less in the threshold equivalent seriesresistance value ESRth as an acceptable equivalent series resistancevalue ESRp. More specifically, the wireless power transmitter maydetermine a value increased by 20% in the threshold equivalent seriesresistance value as the acceptable equivalent series resistance value.

The wireless charging method in the wireless power transmitter mayinclude determining whether the measured equivalent series resistancevalue is less than or equal to the determined acceptable equivalentseries resistance value (S1105).

When the equivalent series resistance value is less than or equal to theacceptable equivalent series resistance value, the wireless powertransmitter may determine to perform wireless charging (S1106). When theequivalent series resistance value exceeds the acceptable equivalentseries resistance value, the wireless power transmitter may determine tostop wireless charging (S1114). For example, as shown in FIG. 11 , theequivalent series resistance measured in the wireless power transmittermay be a first equivalent series resistance value ESR1, a secondequivalent series resistance value ESR2, and a third equivalent seriesresistance value ESR3. When measured as the first equivalent seriesresistance value ESR1, since there is a very high probability that aforeign object is not present between the wireless power transmitter andthe wireless power receiver, it is possible to determine that theforeign object is not present. When measured as the third equivalentseries resistance value ESR3, since the third equivalent seriesresistance value (ESR3) is very higher than the threshold equivalentseries resistance value ESRth, and there is a very high probability thatthe foreign object is not present between the wireless power transmitterand the wireless power receiver, it is possible to determine that theforeign object is present. When measured as the second equivalent seriesresistance value ESR2, since the second equivalent series resistancevalue ESR2 is between the threshold equivalent series resistance valueESRth and the acceptable equivalent series resistance value ESRp, it maybe misrecognized as being the foreign object is present between thewireless power transmitter and the wireless power receiver. In order toprevent this, the wireless power transmitter may perform wirelesscharging when the measured equivalent series resistance value is greaterthan or equal to the acceptable equivalent series resistance value.Thereafter, the wireless power transmitter may determine more accuratelywhether a foreign object is present or not by performing detection of asecond foreign object in the power transfer phase of S1111. Therefore,the wireless power transmitter may determine to perform wirelesscharging when the equivalent series resistance value is less than orequal to the acceptable equivalent series resistance value. Accordingly,another embodiment may accurately determine the foreign object. Inaddition, another embodiment may accurately determine the foreign objectto prevent a heat generation phenomenon, a reduction phenomenon incharging efficiency, a loss of power consumption. In addition, anotherembodiment may solve a problem that the wireless charging is notperformed by erroneously recognizing that a foreign object is present inthe related art.

When the wireless power transmitter determines to perform wirelesscharging, the ACK packet may be transmitted to the wireless powerreceiver in response to receiving the FOD status packet (S1107).

The wireless charging method in the wireless power transmitter mayinclude a step of determining whether the wireless power transmitter hasan equivalent series resistance value less than or equal to a thresholdequivalent series resistance value (S1108). More specifically, thewireless power transmitter may determine whether the equivalent seriesresistance value is less than or equal to the threshold equivalentseries resistance value in order to determine whether to performcalibration after transition to the calibration phase after determiningto perform wireless charging in the negotiation phase.

The wireless charging method in the wireless power transmitter mayinclude a step of performing calibration after transition to thecalibration phase (S1109) when the equivalent series resistance value isless than or equal to the threshold equivalent series resistance value.As an example, in performing the calibration, the wireless powertransmitter may predict power loss by using the received power value ofthe wireless power receiver of the received power packet and themeasured transmission power value. In addition, in performing thecalibration the wireless power transmitter may increase strength of thetransmission power by using the predicted power loss value.

In the wireless charging method in the wireless power transmitter, whenthe equivalent series resistance value exceeds the threshold equivalentseries resistance value, the wireless power transmitter may transitionto the power transfer phase (S910) without a calibration phase.

The wireless charging method in the wireless power transmitter mayinclude performing the second foreign object detection (S1111) whenreceiving the received power packet after transition to the powertransfer phase. The wireless power transmitter may stop wirelesscharging when it is determined that the foreign object has been detectedby performing the second foreign object detection (S1112, S1113). Inaddition, the wireless power transmitter may maintain the power transferphase when it is determined that the foreign object is not detected byperforming the second foreign object detection, and may perform thesecond foreign object detection again when the received power packet isreceived (S1112, S1111). As an example, in the power transfer phase, thewireless power transmitter may determine power loss using the receivedpower value of the received power packet and the measured transmissionpower value, and may detect the presence or absence of a foreign objectaccording to a power loss value. When the power loss value exceeds apredetermined threshold power loss value, the wireless power transmittermay determine that a foreign object is present. In this case, thewireless power transmitter may transmit an NAK packet to the wirelesspower receiver in response to the received power packet in order to stopcharging. Thereafter, the wireless power transmitter may stop wirelesscharging. As another example, the wireless power transmitter may detectthe presence or absence of a foreign object using a measured internaltemperature value regardless of whether or not the received power packetis received. That is, when the internal temperature value exceeds apredetermined threshold temperature value, it is possible to determinethat a foreign object is present. In this case, the wireless powertransmitter may stop wireless charging. Therefore, in still anotherembodiment, even though foreign object detection is suspected in thenegotiation phase, the wireless charging is performed without stoppingthe wireless charging, and then the foreign object is detected again inthe power transfer phase to accurately determine whether the foreignobject is present.

When the wireless power transmitter determines to stop wireless chargingin S1114, the wireless power transmitter may transmit an NAK packet tothe wireless power receiver in response to receiving the FOD statuspacket (S1115). Thereafter, the wireless power transmitter may stopwireless charging (S1113).

FIGS. 12A and 12B are views for describing a wireless charging method ina wireless power transmitter according to still another embodiment.

Referring to FIGS. 12A and 12B, the wireless charging method in thewireless power transmitter may include measuring a quality factor value,a peak frequency value, and an equivalent series resistance value beforea ping phase (S1101). As an example, the wireless power transmitter maymeasure the quality factor value, the peak frequency value, and theequivalent series resistance value using a sensor in a selection phase.

The wireless charging method in the wireless power transmitter mayinclude receiving an FOD status packet including a reference qualityfactor value and a reference peak frequency value (S1202). As anexample, the wireless power transmitter may receive the FOD statuspacket using a communication unit in a negotiation phase. The referencequality factor value and the reference peak frequency value may be aquality factor value and a peak frequency value stored in the wirelesspower receiver.

The wireless charging method in the wireless power transmitter mayinclude determining a threshold quality factor value, a thresholdfrequency value, and a threshold equivalent series resistance value(S1203). More specifically, the wireless power transmitter may calculatethe threshold quality factor value using a received reference qualityfactor value. As an example, the wireless power transmitter maydetermine a value decreased by 10% in the reference quality factor valueas the threshold quality factor value. 10% is a tolerance of thereference quality factor value, and when a foreign object is present,the foreign object may be detected by using that a measured qualityfactor value which is at least the tolerance or more becomes smallerthan the reference quality factor value. In addition, the wireless powertransmitter may calculate a threshold peak frequency value using areceived reference frequency value. As an example, the wireless powertransmitter may determine a value increased by 10% in the referencefrequency value as the threshold frequency value. 10% is a tolerance ofthe reference peak frequency value, and when a foreign object ispresent, the foreign object may be detected by using that a measuredpeak frequency value which is at least the tolerance or more becomesgreater than the reference peak frequency value. In addition, thewireless power transmitter may determine a reference equivalent seriesresistance value using the received reference quality factor value andreference peak frequency value. As an example, the wireless powertransmitter may determine a value increased by 10% in the referenceequivalent series resistance value as a threshold equivalent seriesresistance value ESRth. As another example, the wireless powertransmitter may determine a maximum value ESRmax of the referenceequivalent series resistance as the threshold equivalent seriesresistance ESRth. 10% is a tolerance of the reference equivalent seriesresistance value, and when a foreign object is present, the foreignobject may be detected by using that a measured equivalent seriesresistance value which is at least the tolerance or more becomes greaterthan the reference equivalent series resistance value.

The wireless charging method in the wireless power transmitter mayinclude determining an acceptable quality factor value, an acceptablefrequency value, and an acceptable equivalent series resistance value(S1204). More specifically, the wireless power transmitter may calculatethe acceptable quality factor value using the threshold quality factorvalue determined as S704 of FIG. 6 . In addition, the wireless powertransmitter may calculate an acceptable peak frequency value using thethreshold peak frequency value determined as S904 in FIG. 8 . Further,the wireless power transmitter may calculate the acceptable equivalentseries resistance value using the threshold equivalent series resistancevalue determined as S1104 in FIG. 10 .

The wireless charging method in the wireless power transmitter mayinclude determining whether a measured quality factor value is greaterthan or equal to the determined quality factor value (S1205). Thewireless power transmitter may determine to stop wireless charging whenthe quality factor value is not greater than or equal to the acceptablequality factor value (S1218).

The wireless charging method in the wireless power transmitter mayinclude determining whether the measured equivalent series resistancevalue is less than or equal to the determined acceptable equivalentseries resistance value when the quality factor value is greater than orequal to the acceptable quality factor value. When the equivalent seriesresistance value is not less than or equal to the acceptable equivalentseries resistance value, the wireless power transmitter may determine tostop wireless charging (S1218).

The wireless charging method in the wireless power transmitter maydetermine to perform wireless charging when the peak frequency value isless than or equal to the acceptable peak frequency value (S1208). Thatis, when a measurement value used for foreign object detection does notreach a threshold value that is a reference for the wireless charging,but reaches an acceptable value, the wireless power transmitter maydetermine to perform wireless charging. Accordingly, still anotherembodiment may determine a foreign object accurately. In addition, stillanother embodiment may accurately determine the foreign object toprevent a heat generation phenomenon, a decrease phenomenon in chargingefficiency, and a loss of power consumption, and a waste of powerconsumption. Further, still another embodiment may solve a problem inwhich wireless charging is not performed by erroneously recognizing thata foreign object is present in the related art.

When the wireless power transmitter determines to perform wirelesscharging, the ACK packet may be transmitted to the wireless powerreceiver in response to receiving the FOD status packet (S1209).

The wireless charging method in the wireless power transmitter mayinclude determining whether the wireless power transmitter has a qualityfactor value greater than or equal to a threshold quality factor value(S1210). When the quality factor value is not greater than or equal tothe threshold quality factor value, the wireless power transmitter maytransition to a power transfer phase S1214 without a calibration phase.

The wireless charging method in the wireless power transmitter mayinclude determining whether the equivalent series resistance value isgreater than or equal to a threshold equivalent series resistance valuewhen the quality factor value is greater than or equal to the thresholdquality factor value (S1211). When the equivalent series resistancevalue is not less than or equal to the threshold equivalent seriesresistance value, the wireless power transmitter may transition to thepower transfer phase without the calibration phase (S1214).

The wireless charging method in the wireless power transmitter mayinclude determining whether the peak frequency value greater than orequal to a threshold peak frequency value when the equivalent seriesresistance value is less than or equal to the threshold equivalentseries resistance value (S1212). When the peak frequency value is notless than or equal to the threshold peak frequency value, the wirelesspower transmitter may transition to the power transfer phase without thecalibration phase (S1214).

The wireless charging method in the wireless power transmitter mayinclude performing calibration after transition to a calibration phasewhen the peak frequency value is less than or equal to the thresholdpeak frequency value (S1213).

The wireless charging method in the wireless power transmitter mayinclude performing the second foreign object detection (S1215) whenreceiving the received power packet after transition to the powertransfer phase. The wireless power transmitter may stop wirelesscharging when it is determined that the foreign object has been detectedby performing the second foreign object detection (S1216, S1217). Inaddition, the wireless power transmitter may maintain the power transferphase when it is determined that the foreign object is not detected byperforming the second foreign object detection, and may perform thesecond foreign object detection again when the received power packet isreceived (S1216, S1215). As an example, in the power transfer phase, thewireless power transmitter may determine power loss using the receivedpower value of the received power packet and the measured transmissionpower value, and may detect the presence or absence of a foreign objectaccording to a power loss value. When the power loss value exceeds apredetermined threshold power loss value, the wireless power transmittermay determine that a foreign object is present. In this case, thewireless power transmitter may transmit an NAK packet to the wirelesspower receiver in response to the received power packet in order to stopcharging. Thereafter, the wireless power transmitter may stop wirelesscharging. As another example, the wireless power transmitter may detectthe presence or absence of a foreign object using a measured internaltemperature value regardless of whether or not the received power packetis received. That is, when the internal temperature value exceeds apredetermined threshold temperature value, it is possible to determinethat a foreign object is present. In this case, the wireless powertransmitter may stop wireless charging. Therefore, in anotherembodiment, even though foreign object detection is suspected in thenegotiation phase, the wireless charging is performed without stoppingthe wireless charging, and then the foreign object is detected again inthe power transfer phase to accurately determine whether the foreignobject is present.

When the wireless power transmitter determines to stop wireless chargingin S1218, the wireless power transmitter may transmit the NAK packet tothe wireless power receiver in response to receiving the FOD statuspacket (S1219). Thereafter, the wireless power transmitter may stopwireless charging (S1217).

FIG. 13 is a view for describing a wireless charging method on awireless charging system according to still another embodiment.

Referring to FIG. 13 , a wireless power transmitter 1310 may transmit ananalog ping to a wireless power receiver 1320 in a selection phase(S1301).

The wireless power transmitter 1310 may measure a quality factor valuebefore a ping phase (S1302). As an example, the wireless powertransmitter 1310 may measure the quality factor value in the selectionphase (S1302).

The wireless power transmitter 1310 may transition from the selectionphase to the ping phase when an object is detected. The wireless powertransmitter 1310 activates the wireless power receiver 1320, and maytransmit a digital ping in order to identify whether a receiver is thewireless power receiver 1320 (S1303). The wireless power receiver 1320may transmit a signal strength packet in response to the digital ping(S1304).

When the ping phase is completed, in an identification and configurationphase, the wireless power receiver 1320 may transmit an identificationpacket for informing identification information and a configurationpacket for informing configuration information (S1305 to S1306). When anegotiation field value of the configuration packet is a valueindicating to perform a negotiation phase, the wireless powertransmitter 1310 and the wireless power receiver 1320 may transition tothe negotiation phase.

In the negotiation phase, the wireless power receiver 1320 may transmitan FOD status packet for FO detection (S1307). The FOD status packet mayinclude a reference quality factor value.

The wireless power transmitter 1310 may perform foreign object detection(S1308). The foreign object detection may detect the foreign object byusing a measured quality factor value and information of a received FODstate packet. The foreign object detection follows descriptions of thewireless charging method of FIGS. 14A and 15A.

The wireless power transmitter 1310 may transmit an NAK to the wirelesspower receiver 1320 in response to the FOD status packet when it isdetermined that a foreign object is present after performing the firstforeign object detection (S1309). Conversely, the wireless powertransmitter 1310 may transmit an ACK to the wireless power receiver 1320in response to the FOD status packet when it is determined that theforeign object is not present after performing the first foreign objectdetection.

When the NAK is transmitted, the wireless power transmitter 1310 maydetermine whether to perform wireless charging (S1310). Thedetermination of whether to perform wireless charging may use themeasured quality factor value and the information of the received FODstatus packet. The determination of whether to perform wireless chargingfollows descriptions of the wireless charging methods of FIGS. 14A and15B.

The wireless power receiver 1320 may transmit a general request packetrequesting a power transmitter capability packet for a powertransmission contract (S1311).

When the wireless power transmitter 1320 determines to perform wirelesscharging after transmitting the NAK, the wireless power transmitter 1320may transmit the power transmitter capability packet in response to thegeneral request packet (S1312). In this case, a guaranteed power of thepower transmitter capability packet may be a second guaranteed powervalue. Conversely, when the wireless power transmitter 1320 transmitsthe ACK in S1309, the guaranteed power of the power transmittercapability packet may be a first guaranteed power value. As an example,the first guaranteed power value may be greater than the secondguaranteed power value. In particular, the second guaranteed power valuemay be a minimum guaranteed power strength of the wireless powertransmitter 1310. As another example, the first guaranteed power valuemay be greater than 5 W and 15 W or less. The second guaranteed powervalue may be 5 W or less.

The wireless power receiver 1320 may transmit a specific request packetfor proposing a guaranteed power value of the power transmissioncontract based on the second guaranteed power value of the powertransmitter capability packet (S1313). It should be noted that thesecond guaranteed power of the power transmitter capability packet andthe guaranteed power of the power transmission contract may bedistinguished. For example, the wireless power receiver 1320 may requestthe guaranteed power value of the power transmission contract to a valueequal to or less than the second guaranteed power value of the powertransmitter capability packet. For convenience of description, thewireless power receiver 1320 requests the guaranteed power value of thepower transmission contract as the same value as the second guaranteedpower value of the power transmitter capability packet. The wirelesspower transmitter 1310 may transmit an ACK packet in response to aspecific request packet for requesting the guaranteed power value of thepower transmission contract (S1314). That is, the wireless powertransmitter 1310 is in a case in which the guaranteed power value of thepower transmission contract proposed by the wireless power receiver isaccepted. That is, the power transmission contract may be completed tothe second guaranteed power value. Thereafter, when the powertransmission contract is completed, the wireless power receiver 1320 maytransmit a specific request packet for ending the negotiation phase(S1315). The wireless power transmitter 1310 may transmit the ACK packetin response to the specific request packet for ending the negotiationphase (S1316). That is, the wireless power transmitter 1310 may transmitthe ACK packet upon acceptance of the end of the negotiation phase.

The wireless power transmitter 1310 may measure an internal temperaturein the wireless power transmitter such as a charging region aftertransition to a power transfer phase (S1317). In particular, when theNAK is transmitted in response to the FOD status packet in thenegotiation phase, the wireless power transmitter 1310 may transition tothe power transfer phase rather than a calibration phase after ending ofthe negotiation phase.

The wireless power transmitter 1310 may determine whether to increasetransmission power strength (S1319). The determination of the increasein transmit power intensity may use the measured internal temperature, astored preset period and preset temperature. The determination of theincrease in the transmission power strength follows a description of thewireless charging method of FIG. 14B. When the wireless powertransmitter 1310 determines to increase the transmission power strength,a renegotiation phase may be performed. More specifically, the wirelesspower receiver 1320 may transmit the received power packet to thewireless power transmitter 1310 (S1319). In this case, the receivedpower packet may be a received power packet of 24 bits. When thewireless power transmitter 1310 determines to increase the transmissionpower strength, the wireless power transmitter 1310 may transmit the NAKpacket in response to the received power packet (S1320). Thereafter, thewireless power transmitter 1310 may receive a renegotiation packet andtransmit the ACK packet that accepts the transition to the renegotiationphase (S1321 to S1322). The wireless power receiver 1320 may transmitthe general request packet requesting the power transmitter capabilitypacket (S1323). The wireless power transmitter 1310 may transmit thepower transmitter capability packet in response to the general requestpacket (S1324). In this case, the guaranteed power of the powertransmitter capability packet may be a third guaranteed power value. Asan example, the third guaranteed power value may be greater than thesecond guaranteed power value. As another example, the third guaranteedpower value may be greater than 5 W and 15 W or less. The wireless powerreceiver 1320 may transmit the specific request packet for proposing aguaranteed power value of the power transmission contract based on thethird guaranteed power value of the power transmitter capability packet(S1325). It should be noted that the guaranteed power of the powertransmitter capability packet and the guaranteed power of the powertransmission contract may be distinguished. For example, the wirelesspower receiver 1320 may propose the guaranteed power value of the powertransmission contract to a value equal to or less than the thirdguaranteed power value of the power transmitter capability packet. Forconvenience of description, the wireless power receiver 1320 proposesthe guaranteed power value of the power transmission contract as thesame value as the third guaranteed power value of the power transmittercapability packet. The wireless power transmitter 1310 may transmit anACK packet in response to a specific request packet for proposing aguaranteed power value of the power transmission contract (S1326). Thatis, the wireless power transmitter 1310 is in a case in which theguaranteed power value of the power transmission contract proposed bythe wireless power receiver is accepted. That is, the power transmissioncontract may be completed to the third guaranteed power value.Thereafter, when the power transmission contract is completed, thewireless power receiver 1320 may transmit a specific request packet forending the renegotiation phase (S1327). The wireless power transmitter1310 may transmit the ACK packet in response to the specific requestpacket for ending the renegotiation phase (S1327). That is, the wirelesspower transmitter 1310 may transmit the ACK packet upon acceptance ofthe end of the negotiation phase. The wireless power transmitter 1310and the wireless power receiver 1320 may transition to the powertransfer phase to perform wireless charging with the third guaranteedpower.

Therefore, the wireless charging system according to the embodiment mayprovide a wireless charging method and an apparatus and system therefor.In addition, the wireless charging system according to the embodimentmay determine a foreign object accurately. Further, the wirelesscharging system according to the embodiment may accurately determine aforeign object to prevent a heat generation phenomenon, a decrease incharging efficiency, and a loss of power consumption.

FIGS. 14A and 14B are views for describing a wireless charging method ina wireless power transmitter according to still another embodiment ofFIG. 13 , FIG. 15A is a view for describing a foreign object detectionmethod of the wireless charging method of FIG. 14A, and FIG. 15B is aview describing a method of determining whether to perform wirelesscharging in the wireless charging method of FIG. 14A.

Referring to FIGS. 14A and 14B, the wireless charging method in thewireless power transmitter may include sensing an object in a chargingregion (S1401). More specifically, the wireless power transmitter maysense the object based on a change in current of a transmission coil bytransmitting an analog ping.

The wireless charging method in the wireless power transmitter mayinclude measuring a quality factor value before a ping phase (S1402). Asan example, the wireless power transmitter may measure the qualityfactor value using a sensor in a selection phase.

The wireless charging method in the wireless power transmitter mayinclude receiving information including a reference quality factor value(S1403). More specifically, the wireless power transmitter may receivean FOD status packet including the reference quality factor value.

The wireless charging method in the wireless power transmitter mayinclude detecting a foreign object (S1404 to S1405) using the measuredquality factor value and reference quality factor value. As an example,as shown in FIG. 15A, the detecting of the foreign object may includedetermining a threshold quality factor value (S1511). More specifically,the wireless power transmitter may calculate the threshold qualityfactor value using the received reference quality factor value. Thewireless power transmitter may determine a value less than at least 10%in the reference quality factor value as a threshold quality factorvalue. 10% is a tolerance of the reference quality factor value, andwhen a foreign object is present, the foreign object may be detected byusing that a measured quality factor value which is at least thetolerance or more becomes smaller than the reference quality factorvalue. In addition, the detecting of the foreign object detection mayinclude determining whether the measured quality factor value is greaterthan or equal to the threshold quality factor value (S1512). When themeasured quality factor value is greater than or equal to the thresholdquality factor value, the wireless power transmitter may determine thatthe foreign object is not detected (S1513). Further, when the measuredquality factor value is less than the threshold quality factor value,the wireless power transmitter may determine that the foreign object isdetected (S1514).

The wireless charging method in the wireless power transmitter maytransmit an ACK to the wireless power receiver when it is determinedthat the foreign object is not detected (S1406). That is, the wirelesspower transmitter may transmit an ACK packet to the wireless powerreceiver in response to receiving the FOD status packet.

The wireless charging method in the wireless power transmitter mayinclude transmitting information including a first guaranteed powervalue to the wireless power transmitter when the ACK is transmitted(S1407). In this case, the wireless power transmitter may execute apower transmission contract based on the first guaranteed power valuewith the wireless power receiver. As an example, the first guaranteedpower value may be greater than 5 W.

The wireless charging method in the wireless power transmitter mayinclude performing calibration after transition to a calibration phase(S1408) when information including the first guaranteed power value istransmitted. As an example, in performing the calibration, the wirelesspower transmitter may predict power loss by using the received powervalue of the wireless power receiver of the received power packet andthe measured transmission power value. In addition, in performing thecalibration, the wireless power transmitter may increase strength of thetransmission power by using the predicted power loss value.

The wireless charging method in the wireless power transmitter mayinclude performing wireless charging with the first guaranteed power bytransitioning to a power transfer phase after performing the calibration(S1409). In this case, the performing of wireless charging with thefirst guaranteed power may refer to performing wireless chargingaccording to the guaranteed power value according to the executed powertransmission contract based on the first guaranteed power value.

The wireless charging method in the wireless power transmitter maytransmit the NAK to the wireless power receiver when it is determinedthat a foreign object is not detected in S1706 (S1410). That is, thewireless power transmitter may transmit the NAK packet to the wirelesspower receiver in response to receiving the FOD status packet.

The wireless charging method in the wireless power transmitter mayinclude determining whether to perform wireless charging (S1411 toS1412) when transmitting the NAK. As an example, as shown in FIG. 15B,the determining of whether to perform wireless charging may includedetermining an acceptable quality factor value (S1521). Morespecifically, the wireless power transmitter may calculate theacceptable quality factor value using the determined threshold qualityfactor value. As an example, as shown in FIG. 7 , the wireless powertransmitter may determine a value reduced by more than 0% and 20% orless in the threshold quality factor value Qth as an acceptable qualityfactor value Qp. More specifically, the wireless power transmitter maydetermine a value reduced by 20% in the threshold quality factor valueas the acceptable quality factor value. The determining of whether toperform wireless charging may include determining whether the measuredquality factor value is greater than or equal to the determinedacceptable quality factor value (S1522). When the measured qualityfactor value is greater than or equal to the acceptable quality factorvalue, the wireless power transmitter may determine to perform wirelesscharging (S1523). In addition, when the measured quality factor value isless than the acceptable quality factor value, the wireless powertransmitter may determine that wireless charging is not performed(S1524). For example, as shown in FIG. 8 , when a frequency of thetransmission power is a first frequency, the quality factor measured inthe wireless power transmitter may be a first quality factor value Q1, asecond quality factor value Q2, and a third quality factor value Q3.When measured as the first quality factor value Q1, since there is avery high probability that a foreign object is not present between thewireless power transmitter and the wireless power receiver, it ispossible to determine that the foreign object is not present. Whenmeasured as the third quality factor value Q3, since the third qualityfactor value Q3 is very lower than the threshold quality factor valueQth, and there is a very high probability that the foreign object ispresent between the wireless power transmitter and the wireless powerreceiver, it is possible to determine that the foreign object ispresent. When measured as the second quality factor value Q2, since thesecond quality factor value Q2 is between the threshold quality factorvalue Qth and the acceptable quality factor value Qp, it may bemisrecognized that the foreign object is present between the wirelesspower transmitter and the wireless power receiver. In order to preventthis, the wireless power transmitter may perform wireless charging whenthe measured quality factor value is greater than or equal to theacceptable quality factor value. Thereafter, the wireless powertransmitter may determine again whether to stop wireless charging basedon the internal temperature in S1417. Therefore, the wireless powertransmitter may determine to perform wireless charging when the qualityfactor value is greater than or equal to the acceptable quality factorvalue. Accordingly, still another embodiment may accurately determinethe foreign object. In addition, still another embodiment may accuratelydetermine the foreign object to prevent a heat generation phenomenon, areduction phenomenon in charging efficiency, a loss of powerconsumption. In addition, still another embodiment may solve a problemthat the wireless charging is not performed by erroneously recognizingthat a foreign object is present in the related art.

The wireless charging method in the wireless power transmitter mayinclude stopping wireless charging (S1413) when it is determined thatthe wireless power transmitter does not perform wireless charging. Morespecifically, in this case, the wireless power transmitter maytransition to the selection phase after a predetermined time has passedin the negotiation phase.

The wireless charging method in the wireless power transmitter mayinclude transmitting information including a second guaranteed powervalue to the wireless power receiver (S1414) when it is determined thatwireless charging is to be performed. In this case, the wireless powertransmitter may have the power transmission contract based on the secondguaranteed power value with the wireless power receiver. As an example,the first guaranteed power value may be greater than the secondguaranteed power value. In particular, the second guaranteed power valuemay be a minimum guaranteed power strength of the wireless powertransmitter. As another example, the second guaranteed power value maybe 5 W or less.

The wireless charging method in the wireless power transmitter mayinclude performing wireless charging with the second guaranteed power bytransitioning to a power transfer phase (S1415) without a calibrationphase when information including the second guaranteed power value istransmitted. In this case, the performing of wireless charging with thesecond guaranteed power may refer to performing wireless chargingaccording to the guaranteed power value according to the executed powertransmission contract based on the second guaranteed power value.

The following is an example of foreign object detection in a powertransfer phase after a foreign object is detected before the powertransfer phase. When it is determined that the foreign object ispresent, heat generation may be further caused by the foreign object,and thus overheat protection means needs to be strengthened.Alternatively, since the foreign object may absorb a large amount ofpower, it is possible to detect the foreign object by comparing a presetpower loss value with a difference between power received by thereceiver and transmission power. At this time, the preset power lossvalue may be smaller than a power loss threshold value in a state inwhich it is determined that the foreign object is present.

For the enhanced overheat protection means, the wireless charging methodin the wireless power transmitter may include measuring a temperature ofthe wireless power transmitter such as a charging region (S1416). Thetemperature of the wireless power transmitter may refer to a surfacetemperature or a temperature sensed by a sensor in the transmitter.

The wireless charging method in the wireless power transmitter mayinclude the determining of whether an internal temperature measured fora preset period is less than a preset temperature (S1417). The presetperiod and the preset temperature may be stored values.

The wireless charging method in the wireless power transmitter mayinclude stopping wireless charging when the internal temperature isgreater than or equal to the preset temperature for the preset period(S1418). More specifically, in this case, the wireless power transmittermay transition to the selection phase after a predetermined time haspassed in the power transfer phase. That is, the wireless powertransmitter stops wireless charging by determining that a foreign objectis present when the internal temperature is greater than or equal to thepreset temperature for the preset period. Alternatively, renegotiationmay be performed to lower transmission power. As an example, thewireless power transmitter may transmit an NAK packet to the wirelesspower receiver in response to the received power packet, and then thewireless power transmitter may transmit a renegotiation packet to thewireless power transmitter to perform the renegotiation phase. That is,the wireless power transmitter may decrease transmission power strengthby determining that a foreign object is present when the internaltemperature is greater than or equal to the preset temperature for thepreset period.

The wireless charging method in the wireless power transmitter mayinclude performing a renegotiation phase when the internal temperatureis less than the preset temperature for the preset period (S1419). As anexample, the wireless power transmitter may transmit an NAK packet tothe wireless power receiver in response to the received power packet,and then the wireless power transmitter may transmit a renegotiationpacket to the wireless power transmitter to perform the renegotiationphase. That is, the wireless power transmitter may increase transmissionpower strength by determining that a foreign object is not present whenthe internal temperature is less than the preset temperature for thepreset period.

The wireless charging method in the wireless power transmitter mayinclude transmitting information including a third guaranteed powervalue to the wireless power receiver when transitioning to therenegotiation phase (S1420). In this case, the wireless powertransmitter may execute a power transmission contract based on the thirdguaranteed power value with the wireless power receiver. As an example,the third guaranteed power value may be greater than the secondguaranteed power value. As another example, the third guaranteed powervalue may be greater than 5 W.

The wireless charging method in the wireless power transmitter mayinclude performing wireless charging with the third guaranteed power bytransitioning to the power transfer phase (S1421). In this case, theperforming of wireless charging with the third guaranteed power mayrefer to performing wireless charging according to the guaranteed powervalue according to the power transmission contract based on the thirdguaranteed power value. Accordingly, the wireless power transmitterprotects a system by lowering the transmission power strength bydetermining that a foreign object has been detected in the negotiationphase, but it is possible to increases wireless charging efficiency byincreasing the transmission power strength by determining that theforeign object is not detected finally in the power transfer phase.

In still another embodiment, in transmitting the NAK (s1410), thewireless power receiver may request a minimum power required for thereceiver to charge a battery to the transmitter (negotiation phase).

In addition, when it is determined that a foreign object is not presentafter a predetermined time has passed, the receiver may increase theguaranteed power through renegotiation.

FIG. 16 is a view for describing a wireless charging method on awireless charging system according to still another embodiment.

Referring to FIG. 16 , a wireless power transmitter 1610 may transmit ananalog ping to a wireless power receiver 1620 in a selection phase(S1601).

The wireless power transmitter 1610 may measure a quality factor valuebefore a ping phase (S1602). As an example, the wireless powertransmitter 1610 may measure the quality factor value in the selectionphase (S1602).

The wireless power transmitter 1610 may transition from the selectionphase to the ping phase when an object is detected. The wireless powertransmitter 1610 activates the wireless power receiver 1620, and maytransmit a digital ping in order to identify whether a receiver is thewireless power receiver 1620 (S1603). The wireless power receiver 1620may transmit a signal strength packet in response to the digital ping(S1604).

When the ping phase is completed, in an identification and configurationphase, the wireless power receiver 1620 may transmit an identificationpacket for informing identification information and a configurationpacket for informing configuration information (S1605 to S1606). When anegotiation field value of the configuration packet is a valueindicating to perform a negotiation phase, the wireless powertransmitter 1610 and the wireless power receiver 1620 may transition tothe negotiation phase.

In the negotiation phase, the wireless power receiver 1620 may transmitan FOD status packet for FO detection (S1607). The FOD status packet mayinclude a reference quality factor value.

The wireless power transmitter 1610 may check whether a receivedreference quality factor value is less than a preset quality factorvalue (for example, 50) (S1608). When the reference quality factor valueis less than a preset quality factor value, a step according toperforming first foreign object detection may be performed. When thereference quality factor value is greater than or equal to the presetquality factor value, a step according to performing second foreignobject detection may be performed. That is, as the reference qualityfactor value becomes lower to be less than the preset quality factorvalue, an error in foreign object detection using the quality factorvalue may be large. On the other hand, when the reference quality factorvalue is greater than or equal to the preset quality factor value, theerror in foreign object detection using the quality factor value may besmall. Therefore, it is possible to further increase accuracy of foreignobject detection and reduce unnecessary power consumption by making eachstep of a wireless power transmission method to be different afterdetecting the foreign object according to a size of the referencequality factor value. The method for wireless power transmission afterdetecting foreign objects according to the size of the reference qualityfactor value follows descriptions of FIGS. 17A and 17B.

When the reference quality factor value is less than the preset qualityfactor value, the wireless power transmitter 1610 may perform the firstforeign object detection (S1609). In the first foreign object detection,the foreign object may be detected using a measured quality factor valueand information of a received FOD status packet. The first foreignobject detection follows descriptions of the wireless charging method ofFIGS. 17A and 15A.

The wireless power transmitter 1610 may transmit an NAK to the wirelesspower receiver 1620 in response to the FOD status packet when it isdetermined that a foreign object is present after performing the firstforeign object detection (S1610). Conversely, the wireless powertransmitter 1610 may transmit an ACK to the wireless power receiver 1620in response to the FOD status packet when it is determined that theforeign object is not present after performing the first foreign objectdetection.

When the NAK is transmitted, the wireless power transmitter 1610 maydetermine whether to perform wireless charging (S1611). Thedetermination of whether to perform wireless charging may use themeasured quality factor value and the information of the received FODstatus packet. The determination of whether to perform wireless chargingfollows descriptions of the wireless charging methods of FIGS. 16A and15B. On the other hand, when the wireless power transmitter 1610transmits the NAK after the second foreign object detection, thewireless charging may be stopped without determining whether to performwireless charging.

As another example, when the reference quality factor value is less thanthe preset quality factor value of the wireless power transmitter,wireless charging may be stopped. In addition, when the referencequality factor value is greater than or equal to the preset qualityfactor value of the wireless power transmitter, the first foreign objectdetection may be performed.

The wireless power receiver 1620 may transmit a general request packetrequesting a power transmitter capability packet for a powertransmission contract (S1612).

When the wireless power transmitter 1610 determines to perform wirelesscharging after transmitting the NAK, the wireless power transmitter 1610may transmit the power transmitter capability packet in response to thegeneral request packet (S1613). In this case, a guaranteed power of thepower transmitter capability packet may be a second guaranteed powervalue. Conversely, when the wireless power transmitter 1610 transmitsthe ACK in S1610, the guaranteed power of the power transmittercapability packet may be a first guaranteed power value. As an example,the first guaranteed power value may be greater than the secondguaranteed power value. In particular, the second guaranteed power valuemay be a minimum guaranteed power strength of the wireless powertransmitter 1610. As another example, the first guaranteed power valuemay be greater than 5 W and 15 W or less. The second guaranteed powervalue may be 5 W or less.

The wireless power receiver 1620 may transmit a specific request packetfor proposing a guaranteed power value of the power transmissioncontract based on the second guaranteed power value of the powertransmitter capability packet (S1614). It should be noted that thesecond guaranteed power of the power transmitter capability packet andthe guaranteed power of the power transmission contract may bedistinguished. For example, the wireless power receiver 1620 may requestthe guaranteed power value of the power transmission contract to a valueequal to or less than the second guaranteed power value of the powertransmitter capability packet. For convenience of description, thewireless power receiver 1620 requests the guaranteed power value of thepower transmission contract as the same value as the second guaranteedpower value of the power transmitter capability packet. The wirelesspower transmitter 1610 may transmit an ACK packet in response to aspecific request packet for requesting the guaranteed power value of thepower transmission contract (S1615). That is, the wireless powertransmitter 1610 is in a case in which the guaranteed power value of thepower transmission contract proposed by the wireless power receiver isaccepted. That is, the power transmission contract may be completed tothe second guaranteed power value. Thereafter, when the powertransmission contract is completed, the wireless power receiver 1620 maytransmit a specific request packet for ending the negotiation phase(S1616). The wireless power transmitter 1610 may transmit the ACK packetin response to the specific request packet for ending the negotiationphase (S1617). That is, the wireless power transmitter 1610 may transmitthe ACK packet upon acceptance of the end of the negotiation phase.

The wireless power transmitter 1610 may measure an internal temperaturein the wireless power transmitter such as a charging region aftertransition to a power transfer phase (S1618). In particular, when theNAK is transmitted in response to the FOD status packet in thenegotiation phase, the wireless power transmitter 1610 may transition tothe power transfer phase rather than a calibration phase after ending ofthe negotiation phase.

The wireless power transmitter 1610 may determine whether to increasetransmission power strength (S1619). The determination of the increasein transmit power intensity may use the measured internal temperature, astored preset period and preset temperature. The determination of theincrease in the transmission power strength follows a description of thewireless charging method of FIG. 17B. When the wireless powertransmitter 1610 determines to increase the transmission power strength,a renegotiation phase may be performed. More specifically, the wirelesspower receiver 1620 may transmit the received power packet to thewireless power transmitter 1610 (S1620). In this case, the receivedpower packet may be a received power packet of 24 bits. When thewireless power transmitter 1610 determines to increase the transmissionpower strength, the wireless power transmitter 1610 may transmit the NAKpacket in response to the received power packet (S1621). Thereafter, thewireless power transmitter 1610 may receive a renegotiation packet andtransmit the ACK packet that accepts the transition to the renegotiationphase (S1622 to S1623). The wireless power receiver 1620 may transmitthe general request packet requesting the power transmitter capabilitypacket (S1624). The wireless power transmitter 1610 may transmit thepower transmitter capability packet in response to the general requestpacket (S1625). In this case, the guaranteed power of the powertransmitter capability packet may be a third guaranteed power value. Asan example, the third guaranteed power value may be greater than thesecond guaranteed power value. As another example, the third guaranteedpower value may be greater than 5 W and 15 W or less. The wireless powerreceiver 1620 may transmit the specific request packet for proposing aguaranteed power value of the power transmission contract based on thethird guaranteed power value of the power transmitter capability packet(S1626). It should be noted that the guaranteed power of the powertransmitter capability packet and the guaranteed power of the powertransmission contract may be distinguished. For example, the wirelesspower receiver 1620 may propose the guaranteed power value of the powertransmission contract to a value equal to or less than the thirdguaranteed power value of the power transmitter capability packet. Forconvenience of description, the wireless power receiver 1620 proposesthe guaranteed power value of the power transmission contract as thesame value as the third guaranteed power value of the power transmittercapability packet. The wireless power transmitter 1610 may transmit anACK packet in response to a specific request packet for proposing aguaranteed power value of the power transmission contract (S1627). Thatis, the wireless power transmitter 1610 is in a case in which theguaranteed power value of the power transmission contract proposed bythe wireless power receiver is accepted. That is, the power transmissioncontract may be completed to the third guaranteed power value.Thereafter, when the power transmission contract is completed, thewireless power receiver 1620 may transmit a specific request packet forending the renegotiation phase (S1628). The wireless power transmitter1610 may transmit the ACK packet in response to the specific requestpacket for ending the renegotiation phase (S1628). That is, the wirelesspower transmitter 1610 may transmit the ACK packet upon acceptance ofthe end of the negotiation phase. The wireless power transmitter 1610and the wireless power receiver 1620 may transition to the powertransfer phase to perform wireless charging with the third guaranteedpower.

Therefore, the wireless charging system according to the embodiment mayprovide a wireless charging method and an apparatus and system therefor.In addition, the wireless charging system according to the embodimentmay determine a foreign object accurately. Further, the wirelesscharging system according to the embodiment may accurately determine aforeign object to prevent a heat generation phenomenon, a decrease incharging efficiency, and a loss of power consumption.

FIGS. 17A and 17B are views for describing a wireless charging method ina wireless power transmitter according to still another embodiment ofFIG. 16 .

Referring to FIGS. 17A and 17B, the wireless charging method in thewireless power transmitter may include sensing an object in a chargingregion (S1701). More specifically, the wireless power transmitter maysense the object based on a change in current of a transmission coil bytransmitting an analog ping.

The wireless charging method in the wireless power transmitter mayinclude measuring a quality factor value before a ping phase (S1702). Asan example, the wireless power transmitter may measure the qualityfactor value using a sensor in a selection phase.

The wireless charging method in the wireless power transmitter mayinclude receiving information including a reference quality factor value(S1703). More specifically, the wireless power transmitter may receivean FOD status packet including the reference quality factor value. As anexample, the wireless power transmitter may receive the FOD statuspacket using a communication unit in a negotiation phase. The referencequality factor value is a quality factor value stored in a wirelesspower receiver and may be a quality factor value measured in a specificcoil unit.

The wireless charging method in the wireless power transmitter mayinclude determining whether the reference quality factor value is lessthan a preset quality factor value (for example, 50) (S1704). When thereference quality factor value is less than the preset quality factorvalue, a step according to performing first foreign object detection maybe performed. When the reference quality factor value is greater than orequal to the preset quality factor value, a step according to performingsecond foreign object detection may be performed. That is, as thereference quality factor value becomes lower to be less than the presetquality factor value (for example, 50), an error in foreign objectdetection using the quality factor value may be large. On the otherhand, when the reference quality factor value is greater than or equalto the preset quality factor value, the error in foreign objectdetection using the quality factor value may be small. Therefore, it ispossible to further increase accuracy of foreign object detection andreduce unnecessary power consumption by making each step of a wirelesspower transmission method to be different after detecting the foreignobject according to a size of the reference quality factor value.

The wireless charging method in the wireless power transmitter mayinclude detecting the first foreign object using a measured qualityfactor value and the reference quality factor value when the referencequality factor value is less than the preset quality factor value (S1705to S1706).

As another example, when the reference quality factor value is less thanthe preset quality factor value of the wireless power transmitter,wireless charging may be stopped. When the reference quality factorvalue is greater than or equal to the preset quality factor value of thewireless power transmitter, the first foreign object detection may beperformed.

As another example, the wireless power transmitter may modulate apositive acknowledge (ACK) signal, a negative acknowledge (NAK) signal,not defined (ND) signal, and a caution (warning) signal to transmit tothe wireless power receiver in response to a foreign object detectionstatus packet. The ACK signal is a response signal for continuing awireless charging procedure when there is no foreign object. The NAKsignal may be a response signal for stopping the wireless chargingprocedure as it is determined that a foreign object is present. Thecaution signal may be used when it is difficult to determine whether aforeign object is present. When it is difficult to determine whether theforeign object is present, it may be a case that the reference qualityfactor value of the wireless power receiver is less than the presetvalue (for example, 50). When a change in the quality factor is reducedby a friendly metal (a phenomenon in which the quality factor dampingdue to electric power leakage is obscured), it may be difficult todetermine whether a foreign object is present only by comparing thereference quality factor value and the measured quality factor value. Atthis time, the caution signal is transmitted, and foreign objectdetection based on power loss may be performed while charging with aminimum guaranteed power.

As another example, the caution signal and the NAK signal may be usedaccording to threshold levels of two reference quality factor values.When the reference quality factor value received from the wireless powerreceiver is between a preset first threshold quality factor value and apreset second threshold quality factor value (less than a firstthreshold value), first foreign object detection is performed, and whenit is determined that a foreign object is present as a result ofperforming the first foreign object detection, the caution signal may betransmitted. When the received reference quality factor value is smallerthan the second threshold quality factor value, the NAK signal may betransmitted.

As an example, as shown in FIG. 15A, the detecting of the foreign objectmay include determining a threshold quality factor value (S1511). Morespecifically, the wireless power transmitter may calculate the thresholdquality factor value using the received reference quality factor value.The wireless power transmitter may determine a value less than at least10% in the reference quality factor value as a threshold quality factorvalue. 10% is a tolerance of the reference quality factor value, andwhen a foreign object is present, the foreign object may be detected byusing that a measured quality factor value which is at least thetolerance or more becomes smaller than the reference quality factorvalue. In addition, the detecting of the foreign object detection mayinclude determining whether the measured quality factor value is greaterthan or equal to the threshold quality factor value (S1512). When themeasured quality factor value is greater than or equal to the thresholdquality factor value, the wireless power transmitter may determine thatthe foreign object is not detected (S1513). Further, when the measuredquality factor value is less than the threshold quality factor value,the wireless power transmitter may determine that the foreign object isdetected (S1514).

The wireless charging method in the wireless power transmitter maytransmit an ACK to the wireless power receiver when it is determinedthat the foreign object is not detected in the first foreign objectdetection (S1707). That is, the wireless power transmitter may transmitan ACK packet to the wireless power receiver in response to receivingthe FOD status packet.

The wireless charging method in the wireless power transmitter mayinclude transmitting information including a first guaranteed powervalue to the wireless power transmitter when the ACK is transmitted(S1708). In this case, the wireless power transmitter may execute apower transmission contract based on the first guaranteed power valuewith the wireless power receiver. As an example, the first guaranteedpower value may be greater than 5 W and 15 W or less.

The wireless charging method in the wireless power transmitter mayinclude performing calibration after transition to a calibration phase(S1709) when information including the first guaranteed power value istransmitted. As an example, in performing the calibration, the wirelesspower transmitter may predict power loss by using the received powervalue of the wireless power receiver of the received power packet andthe measured transmission power value. In addition, in performing thecalibration, the wireless power transmitter may increase strength of thetransmission power by using the predicted power loss value.

The wireless charging method in the wireless power transmitter mayinclude performing wireless charging with the first guaranteed power bytransitioning to a power transfer phase after performing the calibration(S1710). In this case, the performing of wireless charging with thefirst guaranteed power may refer to performing wireless chargingaccording to the guaranteed power value according to the executed powertransmission contract based on the first guaranteed power value.

The wireless charging method in the wireless power transmitter maytransmit the NAK to the wireless power receiver when it is determinedthat a foreign object is not detected in S1706 (S1711). That is, thewireless power transmitter may transmit the NAK packet to the wirelesspower receiver in response to receiving the FOD status packet.

The wireless charging method in the wireless power transmitter mayinclude determining whether to perform wireless charging (S1712 toS1713) when transmitting the NAK in S1711. As an example, as shown inFIG. 15B, the determining of whether to perform wireless charging mayinclude determining an acceptable quality factor value (S1521). Morespecifically, the wireless power transmitter may calculate theacceptable quality factor value using the determined threshold qualityfactor value. As an example, as shown in FIG. 7 , the wireless powertransmitter may determine a value reduced by more than 0% and 20% orless in the threshold quality factor value Qth as an acceptable qualityfactor value Qp. More specifically, the wireless power transmitter maydetermine a value reduced by 20% in the threshold quality factor valueas the acceptable quality factor value. The determining of whether toperform wireless charging may include determining whether the measuredquality factor value is greater than or equal to the determinedacceptable quality factor value (S1522). When the measured qualityfactor value is greater than or equal to the acceptable quality factorvalue, the wireless power transmitter may determine to perform wirelesscharging (S1523). In addition, when the measured quality factor value isless than the acceptable quality factor value, the wireless powertransmitter may determine that wireless charging is not performed(S1524). For example, as shown in FIG. 8 , when a frequency of thetransmission power is a first frequency, the quality factor measured inthe wireless power transmitter may be a first quality factor value Q1, asecond quality factor value Q2, and a third quality factor value Q3.When measured as the first quality factor value Q1, since there is avery high probability that a foreign object is not present between thewireless power transmitter and the wireless power receiver, it ispossible to determine that the foreign object is not present. Whenmeasured as the third quality factor value Q3, since the third qualityfactor value Q3 is very lower than the threshold quality factor valueQth, and there is a very high probability that the foreign object ispresent between the wireless power transmitter and the wireless powerreceiver, it is possible to determine that the foreign object ispresent. When measured as the second quality factor value Q2, since thesecond quality factor value Q2 is between the threshold quality factorvalue Qth and the acceptable quality factor value Qp, it may bemisrecognized that the foreign object is present between the wirelesspower transmitter and the wireless power receiver. In order to preventthis, the wireless power transmitter may perform wireless charging whenthe measured quality factor value is greater than or equal to theacceptable quality factor value. Thereafter, the wireless powertransmitter may determine again whether to stop wireless charging basedon the internal temperature in S1718. Therefore, the wireless powertransmitter may determine to perform wireless charging when the qualityfactor value is greater than or equal to the acceptable quality factorvalue. Accordingly, still another embodiment may accurately determinethe foreign object. In addition, still another embodiment may accuratelydetermine the foreign object to prevent a heat generation phenomenon, areduction phenomenon in charging efficiency, a loss of powerconsumption. In addition, still another embodiment may solve a problemthat the wireless charging is not performed by erroneously recognizingthat a foreign object is present in the related art.

The wireless charging method in the wireless power transmitter mayinclude stopping wireless charging (S1714) when it is determined thatthe wireless power transmitter does not perform wireless charging. Morespecifically, in this case, the wireless power transmitter maytransition to the selection phase after a predetermined time has passedin the negotiation phase.

The wireless charging method in the wireless power transmitter mayinclude transmitting information including a second guaranteed powervalue to the wireless power receiver (S1715) when it is determined thatwireless charging is to be performed. In this case, the wireless powertransmitter may have the power transmission contract based on the secondguaranteed power value with the wireless power receiver. As an example,the first guaranteed power value may be greater than the secondguaranteed power value. In particular, the second guaranteed power valuemay be a minimum guaranteed power strength of the wireless powertransmitter. As another example, the second guaranteed power value maybe 5 W or less.

The wireless charging method in the wireless power transmitter mayinclude performing wireless charging with the second guaranteed power bytransitioning to a power transfer phase (S1716) without a calibrationphase when information including the second guaranteed power value istransmitted. In this case, the performing of wireless charging with thesecond guaranteed power may refer to performing wireless chargingaccording to the guaranteed power value according to the executed powertransmission contract based on the second guaranteed power value.

The wireless charging method in the wireless power transmitter mayinclude measuring an internal temperature in the wireless powertransmitter such as a charging region (S1717).

The wireless charging method in the wireless power transmitter mayinclude determining whether the internal temperature is less than apreset temperature for a preset period (S1718). The preset period andthe preset temperature may be a stored value.

The wireless charging method in the wireless power transmitter mayinclude stopping wireless charging when the internal temperature isgreater than or equal to the preset temperature for the preset period(S1719). More specifically, in this case, the wireless power transmittermay transition to the selection phase after a predetermined time haspassed in the power transfer phase. That is, the wireless powertransmitter stops wireless charging by determining that a foreign objectis present when the internal temperature is greater than or equal to thepreset temperature for the preset period.

The wireless charging method in the wireless power transmitter mayinclude performing a renegotiation phase when the internal temperatureis less than the preset temperature for the preset period (S1720). As anexample, the wireless power transmitter may transmit an NAK packet tothe wireless power receiver in response to the received power packet,and then the wireless power transmitter may transmit a renegotiationpacket to the wireless power transmitter to perform the renegotiationphase. That is, the wireless power transmitter may increase transmissionpower strength by determining that a foreign object is not present whenthe internal temperature is less than the preset temperature for thepreset period.

The wireless charging method in the wireless power transmitter mayinclude transmitting information including a third guaranteed powervalue to the wireless power receiver when transitioning to therenegotiation phase (S1721). In this case, the wireless powertransmitter may execute a power transmission contract based on the thirdguaranteed power value with the wireless power receiver. As an example,the third guaranteed power value may be greater than the secondguaranteed power value. As another example, the third guaranteed powervalue may be greater than 5 W and 15 W or less. In addition, consideringthat the NAK is transmitted by the friendly metal, the third guaranteedpower value may be less than or equal to the first guaranteed powervalue.

The wireless charging method in the wireless power transmitter mayinclude performing wireless charging with the third guaranteed power bytransitioning to the power transfer phase (S1722). In this case, theperforming of wireless charging with the third guaranteed power mayrefer to performing wireless charging according to the guaranteed powervalue according to the power transmission contract based on the thirdguaranteed power value. Accordingly, the wireless power transmitterprotects a system by lowering the transmission power strength bydetermining that a foreign object has been detected in the negotiationphase, but it is possible to increases wireless charging efficiency byincreasing the transmission power strength by determining that theforeign object is not detected finally in the power transfer phase.

The wireless charging method in the wireless power transmitter mayinclude detecting the second foreign object (S1723 to S1724) when thereference quality factor value is not less than 50 in S1704. As anexample, as shown in FIG. 15A, the detecting of the foreign object mayinclude determining a threshold quality factor value (S1511). Morespecifically, the wireless power transmitter may calculate the thresholdquality factor value using the received reference quality factor value.The wireless power transmitter may determine a value less than at least10% in the reference quality factor value as a threshold quality factorvalue. 10% is a tolerance of the reference quality factor value, andwhen a foreign object is present, the foreign object may be detected byusing that a measured quality factor value which is at least thetolerance or more becomes smaller than the reference quality factorvalue. In addition, the detecting of the foreign object may includedetermining whether the measured quality factor value is greater than orequal to the threshold quality factor value (S1512). When the measuredquality factor value is greater than or equal to the threshold qualityfactor value, the wireless power transmitter may determine that theforeign object is not detected (S1513). Further, when the measuredquality factor value is less than the threshold quality factor value,the wireless power transmitter may determine that the foreign object isdetected (S1514).

When it is determined that the foreign object is not detected in thesecond foreign object detection, the wireless power transmitter maytransition to S1707.

The wireless charging method in the wireless power transmitter maytransmit an NAK to the wireless power receiver when it is determinedthat the foreign object is not detected in S1724 (S1725). That is, thewireless power transmitter may transmit the NAK packet to the wirelesspower receiver in response to receiving the FOD status packet.

The wireless charging method in the wireless power transmitter mayinclude stopping wireless charging (S1726) when the NAK is transmittedin S1725. That is, when the wireless power transmitter transmits the NAKafter the second foreign object detection, the wireless charging may bestopped without determining whether to perform the wireless charging.More specifically, in this case, the wireless power transmitter maytransition to the selection phase after a predetermined time has passedin the negotiation phase.

FIG. 18 is a view for describing a wireless charging method in awireless power transmitter according to still another embodiment.

Referring to FIG. 18 , the wireless charging method in the wirelesspower transmitter may include sensing an object in a charging region(S1801). More specifically, the wireless power transmitter may sense theobject based on a change in current of a transmission coil bytransmitting an analog ping.

The wireless charging method in the wireless power transmitter mayinclude measuring a quality factor value before a ping phase (S1802). Asan example, the wireless power transmitter may measure the qualityfactor value using a sensor in a selection phase.

The wireless charging method in the wireless power transmitter mayinclude receiving information including a reference quality factor value(S1803). More specifically, the wireless power transmitter may receivean FOD status packet including the reference quality factor value.

The wireless charging method in the wireless power transmitter mayinclude detecting a foreign object (S1804 to S1805) using the measuredquality factor value and reference quality factor value. As an example,as shown in FIG. 15A, the detecting of the foreign object may includedetermining a threshold quality factor value (S1511). More specifically,the wireless power transmitter may calculate the threshold qualityfactor value using the received reference quality factor value. Thewireless power transmitter may determine a value less than at least 10%in the reference quality factor value as a threshold quality factorvalue. 10% is a tolerance of the reference quality factor value, andwhen a foreign object is present, the foreign object may be detected byusing that a measured quality factor value which is at least thetolerance or more becomes smaller than the reference quality factorvalue. In addition, the detecting of the foreign object detection mayinclude determining whether the measured quality factor value is greaterthan or equal to the threshold quality factor value (S1512). When themeasured quality factor value is greater than or equal to the thresholdquality factor value, the wireless power transmitter may determine thatthe foreign object is not detected (S1513). Further, when the measuredquality factor value is less than the threshold quality factor value,the wireless power transmitter may determine that the foreign object isdetected (S1514).

The wireless charging method in the wireless power transmitter mayinclude transmitting information including a first guaranteed powervalue to the wireless power transmitter when it is determined that theforeign object is not detected (S1807). In this case, the wireless powertransmitter may execute a power transmission contract based on the firstguaranteed power value with the wireless power receiver. As an example,the first guaranteed power value may be greater than 5 W. Thereafter,the wireless power transmitter may transition to a power transfer phaseto perform wireless charging with the first guaranteed power value. Inthis case, the performing of wireless charging with the first guaranteedpower may refer to performing wireless charging according to theguaranteed power value according to the executed power transmissioncontract based on the first guaranteed power value.

The wireless charging method in the wireless power transmitter mayinclude transmitting information including a second guaranteed powervalue to the wireless power receiver when it is determined that aforeign object is detected in S1805 (S1807). In this case, the wirelesspower transmitter may execute a power transmission contract based on thesecond guaranteed power value with the wireless power receiver. As anexample, the first guaranteed power value may be greater than or equalto the second guaranteed power value. In particular, the secondguaranteed power value may be a minimum guaranteed power strength of thewireless power transmitter. As another example, the second guaranteedpower value may be 5 W or less. Thereafter, the wireless powertransmitter may transition to the power transfer phase without acalibration phase to perform wireless charging with the secondguaranteed power. In this case, the performing of wireless charging withthe second guaranteed power may refer to performing wireless chargingaccording to the guaranteed power value according to the powertransmission contract based on the second guaranteed power value. Inaddition, when it is determined that a foreign object is not presentafter a predetermined time has passed, the receiver may increase theguaranteed power through renegotiation.

FIG. 19 is view for describing a wireless charging method on a wirelesscharging system according to still another embodiment.

Referring to FIG. 19 , a wireless power transmitter 1910 may transmit ananalog ping to a wireless power receiver 1920 in a selection phase(S1902).

The wireless power transmitter 1910 may measure a quality factor valuebefore a ping phase (S1602). As an example, the wireless powertransmitter 1910 may measure the quality factor value in the selectionphase.

The wireless power transmitter 1910 may transition from the selectionphase to the ping phase when an object is detected. The wireless powertransmitter 1910 activates the wireless power receiver 1920, and maytransmit a digital ping in order to identify whether a receiver is thewireless power receiver 1920 (S1903). The wireless power receiver 1920may transmit a signal strength packet in response to the digital ping(S1904).

When the ping phase is completed, in an identification and configurationphase, the wireless power receiver 1920 may transmit an identificationpacket for informing identification information and a configurationpacket for informing configuration information (S1905 to S1906). When anegotiation field value of the configuration packet is a valueindicating to perform a negotiation phase, the wireless powertransmitter 1910 and the wireless power receiver 1920 may transition tothe negotiation phase.

In the negotiation phase, the wireless power receiver 1920 may transmitan FOD status packet for FO detection (S1907). The FOD status packet mayinclude a reference quality factor value.

The wireless power transmitter 1910 may perform foreign object detection(S1908). The foreign object detection may detect a foreign object byusing a measured quality factor value and information of the receivedFOD state packet. The foreign object detection follows the descriptionof the wireless charging method of FIG. 20

The wireless power transmitter 1910 may transmit an NAK to the wirelesspower receiver 1920 in response to the FOD status packet when it isdetermined that a foreign object is present after performing foreignobject detection (S1909). Conversely, the wireless power transmitter1910 may transmit an ACK to the wireless power receiver 1920 in responseto the FOD status packet when it is determined that the foreign objectis not present after performing the first foreign object detection. Inaddition, the wireless power transmitter 1910 may stop wireless chargingwhen it is determined that a foreign object is present. That is, thewireless power transmitter 1910 may transition to the selection phaseafter a predetermined time has passed in the negotiation phase.

FIG. 20 is a view for describing a wireless charging method in awireless power transmitter according to one embodiment of FIG. 19 , andFIG. 21 is a view for describing a foreign object detection methodaccording to a quality factor value in FIG. 20 .

Referring to FIG. 20 , the wireless charging method in the wirelesspower transmitter may include sensing an object in a charging region(S2001). More specifically, the wireless power transmitter may sense theobject based on a change in current of a transmission coil bytransmitting an analog ping.

The wireless charging method in the wireless power transmitter mayinclude measuring a quality factor value before a ping phase (S2002). Asan example, the wireless power transmitter may measure the qualityfactor value using a sensor in a selection phase.

The wireless charging method in the wireless power transmitter mayinclude receiving information including a reference quality factor value(S2003). More specifically, the wireless power transmitter may receivean FOD status packet including the reference quality factor value.

The wireless charging method in the wireless power transmitter mayinclude determining a threshold quality factor value (S2004). Morespecifically, the wireless power transmitter may calculate the thresholdquality factor value using the received reference quality factor value.As an example, as shown in FIG. 21 , the wireless power transmitter maydetermine a value less than at least 10% in a reference quality factorvalue Qr as a threshold quality factor value Qth. 10% is a tolerance ofthe reference quality factor value, and when a foreign object ispresent, the foreign object may be detected by using that a measuredquality factor value which is at least the tolerance or more becomessmaller than the reference quality factor value.

The wireless charging method in the wireless power transmitter mayinclude determining whether the measured quality factor value is lessthan or equal to the threshold quality factor value (S2005). Thewireless power transmitter may determine that a foreign object ispresent when the measured quality factor value is less than or equal tothe threshold quality factor value. Conversely, the wireless powertransmitter may determine that the foreign object is not present whenthe measured quality factor value is not less than or equal to thethreshold quality factor value. 21. As an example, as shown in FIG. 21 ,when a frequency of transmission power is a first frequency f1, thequality factor measured in the wireless power transmitter may be a firstquality factor value Q1 and a second quality factor value Q2. Since thefirst quality factor value Q1 is greater than the threshold qualityfactor value Qth, it is possible to determine that a foreign object ispresent between the wireless power transmitter and the wireless powerreceiver. Since the second quality factor value Q2 is less than thethreshold quality factor value Qth, it is possible to determine that aforeign object is present between the wireless power transmitter and thewireless power receiver.

The wireless power transmitter may stop wireless charging when themeasured quality factor value is less than or equal to the thresholdquality factor value (S2006). That is, the wireless power transmittermay stop wireless charging when it is determined that a foreign objectis present. Conversely, the wireless power transmitter may performwireless charging when the measured quality factor value is not lessthan or equal to the threshold quality factor value (S2007). That is,the wireless power transmitter may perform wireless charging when it isdetermined that the foreign object is present.

Therefore, one embodiment may determine a foreign object accurately. Inaddition, one embodiment may accurately determine the foreign object toprevent a heat generation phenomenon, a decrease phenomenon in chargingefficiency, and a loss of power consumption.

FIG. 22 is a view for describing a wireless charging method on awireless charging system according to still another embodiment.

Referring to FIG. 22 , a wireless power transmitter 2210 may transmit ananalog ping to a wireless power receiver 2220 in a selection phase(S2201)

The wireless power transmitter 2210 may measure an equivalent seriesresistance value before a ping phase (S2202). As an example, thewireless power transmitter 2210 may measure the equivalent seriesresistance value in the selection phase (S2202).

The wireless power transmitter 2210 may transition from the selectionphase to the ping phase when an object is detected. The wireless powertransmitter 2210 activates the wireless power receiver 2220, and maytransmit a digital ping in order to identify whether a receiver is thewireless power receiver 2220 (S2203). The wireless power receiver 2220may transmit a signal strength packet in response to the digital ping(S2204).

When the ping phase is completed, in an identification and configurationphase, the wireless power receiver 2220 may transmit an identificationpacket for informing identification information and a configurationpacket for informing configuration information (S2205 to S2206). When anegotiation field value of the configuration packet is a valueindicating to perform a negotiation phase, the wireless powertransmitter 2210 and the wireless power receiver 2220 may transition tothe negotiation phase.

In the negotiation phase, the wireless power receiver 2220 may transmitan FOD status packet for FO detection (S2207). The FOD status packet mayinclude a reference quality factor value.

The wireless power transmitter 2210 may perform the foreign objectdetection (S2208). In the foreign object detection, the foreign objectmay be detected using a measured equivalent series resistance value andinformation of a received FOD state packet. The foreign object detectionfollows a description of the wireless charging method of FIG. 23 .

The wireless power transmitter 2210 may transmit an NAK to the wirelesspower receiver 2220 in response to the FOD status packet when it isdetermined that a foreign object is present after performing firstforeign object detection (S2210). Conversely, the wireless powertransmitter 2210 may transmit an ACK to the wireless power receiver 2220in response to the FOD status packet when it is determined that theforeign object is not present after performing the first foreign objectdetection. In addition, the wireless power transmitter 2210 may stopwireless charging when it is determined that the foreign object is notpresent. That is, the wireless power transmitter 2210 may transition tothe selection phase after a predetermined time has passed in thenegotiation phase.

FIG. 23 is a view for describing a wireless charging method in awireless power transmitter according to another embodiment of FIG. 22 ,and FIG. 24 is a view for describing a foreign object detection methodaccording to an equivalent series resistance value.

Referring to FIG. 23 , the wireless charging method in the wirelesspower transmitter according to one embodiment may include sensing anobject in a charging region (S2301). More specifically, the wirelesspower transmitter may sense the object based on a change in current of atransmission coil by transmitting an analog ping.

The wireless charging method in the wireless power transmitter mayinclude measuring an equivalent series resistance value before a pingphase (S2302). As an example, the wireless power transmitter may measurethe equivalent series resistance value using a sensor in a selectionphase.

The wireless charging method in the wireless power transmitter mayinclude receiving information including a reference quality factor valueand a reference peak frequency value (S2303). More specifically, thewireless power transmitter may receive an FOD status packet includingthe reference quality factor value and the reference peak frequencyvalue. As an example, the wireless power transmitter may receive the FODstatus packet using a communication unit in a negotiation phase. Thereference quality factor value and the reference peak frequency valueare a quality factor value and a peak frequency value stored in awireless power receiver.

The wireless charging method in the wireless power transmitter mayinclude determining a first threshold equivalent series resistance value(S2304). Here, the first threshold equivalent series resistance valuemay be determined based on a reference equivalent series resistancevalue. Since the reference equivalent series resistance value has beendescribed already based on Equations 2 and 3, a detailed descriptionthereof will be omitted.

Referring to FIG. 24 , as an example, the wireless power transmitter maydetermine a value increased by a predetermined ratio in a referenceequivalent series resistance value ESRr as a first threshold equivalentseries resistance value ESRth1. At this time, the predetermined ratiomay be 10%. The wireless power transmitter may determine a valuedecreased by a predetermined ratio in the reference equivalent seriesresistance value ESRr as a second threshold equivalent series resistancevalue ESRth2. At this time, the predetermined ratio may be 10%. 10% is atolerance of the reference equivalent series resistance value, and whena foreign object is present, the foreign object may be detected by usingthat a measured equivalent series resistance value which is at least thetolerance or more becomes greater than the reference equivalent seriesresistance value. As another example, the wireless power transmitter maydetermine a maximum value of the reference equivalent series resistanceESRr as the first threshold equivalent series resistance value ESRth1and a minimum value of the reference equivalent series resistance ESRras the second threshold equivalent series resistance value ESRth2. Asstill another example, the first threshold equivalent series resistancevalue ESRth1 may be a value of 50 mΩ or less, and the second thresholdequivalent series resistance value ESRth2 may be a value of 500 mΩ ormore. As still another example, the first threshold equivalent seriesresistance value ESRth1 may be smaller than the second thresholdequivalent series resistance value ESRth2.

The wireless charging method in the wireless power transmitter mayinclude determining whether a measured equivalent series resistancevalue is greater than or equal to the first threshold equivalent seriesresistance value (S2305). The wireless power transmitter may determinethat a foreign object is present when the measured equivalent seriesresistance value is greater than or equal to the first equivalent seriesresistance value. Conversely, the wireless power transmitter maydetermine that a foreign object is present when the measured equivalentseries resistance value is not greater than or equal to the firstthreshold equivalent series resistance value. As an example, as shown inFIG. 24 , the equivalent series resistance value measured in thewireless power transmitter may be the first equivalent series resistancevalue ESR1 and the second equivalent series resistance value ESR2. Sincethe first equivalent series resistance value ESR1 is smaller than thefirst threshold equivalent series resistance value ESRth1, it ispossible to determine that a foreign object is not present between thewireless power transmitter and the wireless power receiver. Since thesecond equivalent series resistance value ESR2 is greater than the firstthreshold equivalent series resistance value ESRth1, it is possible todetermine that a foreign object is present between the wireless powertransmitter and the wireless power receiver.

The wireless power transmitter may stop wireless charging when themeasured equivalent series resistance value is less than or equal to thefirst threshold equivalent series resistance value (S2306). That is, thewireless power transmitter may stop wireless charging when it isdetermined that a foreign object is present. Conversely, the wirelesspower transmitter may perform wireless charging when the measuredequivalent series resistance value is not less than or equal to thefirst threshold equivalent series resistance value (S2007). That is, thewireless power transmitter may perform wireless charging when it isdetermined that the foreign object is present.

Therefore, another embodiment may determine a foreign object accurately.In addition, another embodiment may accurately determine the foreignobject to prevent a heat generation phenomenon, a decrease phenomenon incharging efficiency, and a loss of power consumption.

FIG. 25 is a view for describing a wireless charging method on awireless charging system according to still another embodiment.

Referring to FIG. 25 , a wireless power transmitter 2510 may transmit ananalog ping to a wireless power receiver 2520 in a selection phase(S2501).

The wireless power transmitter 2510 may measure an equivalent seriesresistance value before a ping phase (S2502). As an example, thewireless power transmitter 2510 may measure the equivalent seriesresistance value in the selection phase (S2502).

In addition, the wireless power transmitter 2510 may measure a peakfrequency value before the ping phase (S2503). As an example, thewireless power transmitter 2510 may measure the peak frequency value inthe selection phase (S2502). As another example, the wireless powertransmitter 2510 may determine an inductance value by measuring the peakfrequency of transmission coil in the selection phase.

The wireless power transmitter 2510 may transition from the selectionphase to the ping phase when an object is detected. The wireless powertransmitter 2510 activates the wireless power receiver 2520, and maytransmit a digital ping in order to identify whether a receiver is thewireless power receiver 2520 (S2504). The wireless power receiver 2520may transmit a signal strength packet in response to the digital ping(S2505).

When the ping phase is completed, in an identification and configurationphase, the wireless power receiver 2520 may transmit an identificationpacket for informing identification information and a configurationpacket for informing configuration information (S2506 to S2510). When anegotiation field value of the configuration packet is a valueindicating to perform a negotiation phase, the wireless powertransmitter 2510 and the wireless power receiver 2520 may transition tothe negotiation phase.

In the negotiation phase, the wireless power receiver 2520 may transmitan FOD status packet for FO detection (S2508). The FOD status packet mayinclude one or more of a reference quality factor value and a referencepeak frequency value.

The wireless power transmitter 2510 may perform the foreign objectdetection (S2509). In the foreign object detection, the foreign objectmay be detected using a measured equivalent series resistance value andinformation of a received FOD state packet. The foreign object detectionfollows the description of the wireless charging method of FIG. 26 .

The wireless power transmitter 2510 may transmit an ACK to the wirelesspower receiver 2520 in response to the FOD status packet when it isdetermined that the foreign object is not present after performing theforeign object detection (S2510). Conversely, the wireless powertransmitter 2510 may transmit an NAK to the wireless power receiver 2520in response to the FOD status packet when it is determined that theforeign object is present after performing the second foreign objectdetection (S2520).

The wireless power receiver 2520 may transmit a general request packetrequesting a power transmitter capability packet for a powertransmission contract (S2511). The wireless power transmitter 2520 maytransmit the power transmitter capability packet in response to thegeneral request packet (S2512). In this case, a guaranteed power of thepower transmitter capability packet may be a first guaranteed powervalue. The wireless power receiver 2520 may transmit a specific requestpacket for proposing a guaranteed power value of the power transmissioncontract based on the second guaranteed power value of the powertransmitter capability packet (S2513). The wireless power transmitter2510 may transmit an ACK packet in response to a specific request packetfor requesting a guaranteed power value of the power transmissioncontract (S2514). That is, the wireless power transmitter 2510 is in acase in which the guaranteed power value of the power transmissioncontract proposed by the wireless power receiver is accepted. That is,the power transmission contract may be completed with the firstguaranteed power value. Thereafter, when the power transmission contractis completed, the wireless power receiver 2520 may transmit a specificrequest packet for ending the negotiation phase (S2515). The wirelesspower transmitter 2510 may transmit an ACK packet in response to thespecific request packet for ending the negotiation phase (S2516). Thatis, the wireless power transmitter 2510 may transmit an ACK packet uponacceptance of the end of the negotiation phase.

In the calibration phase, the wireless power receiver 2520 may transmitthe received power packet to the wireless power transmitter 2510(S2517). In this case, the received power packet may be a 24-bitreceived power packet. The wireless power transmitter 2510 may transmitan ACK packet in response to the received power packet in order toperform wireless charging (S2518).

When the calibration phase is completed, the power transfer phase may beperformed with the first guaranteed power. The wireless power receiver2520 may transmit one or more control error packets in order to controltransmission power of the wireless power transmitter 2510 (S2519). Thewireless power receiver 2520 may transmit the received power packetperiodically or arbitrarily (S2520).

FIG. 26 is a view for describing a wireless charging method in awireless power transmitter according to still another embodiment of FIG.25 , and FIG. 27 is a view for describing a foreign object detectionmethod according to a frequency value of FIG. 26 .

Referring to FIG. 26 , the wireless charging method in the wirelesspower transmitter may include sensing an object in a charging region(S2601). More specifically, the wireless power transmitter may sense theobject based on a change in current of a transmission coil bytransmitting an analog ping.

The wireless charging method in the wireless power transmitter mayinclude measuring an equivalent series resistance value and a peakfrequency value before a ping phase (S2602). As an example, the wirelesspower transmitter may measure the equivalent series resistance valueusing a sensor in a selection phase. In addition, the wireless powertransmitter may measure the peak frequency value of transmission powerusing the sensor in the selection phase.

The wireless charging method in the wireless power transmitter mayinclude receiving information including a reference quality factor valueand a reference peak frequency value (S2603). More specifically, thewireless power transmitter may receive an FOD status packet includingthe reference quality factor value and the reference peak frequencyvalue. As an example, the wireless power transmitter may receive the FODstatus packet using a communication unit in a negotiation phase. Thereference quality factor value and the reference peak frequency valueare a quality factor value and a peak frequency value stored in awireless power receiver.

The wireless charging method in the wireless power transmitter mayinclude determining a second threshold equivalent series resistancevalue and a threshold peak frequency value (S2604). More specifically, amethod of determining the second threshold equivalent series resistancevalue may be the same as a method of determining the second thresholdequivalent series resistance value of FIG. 23 . The wireless powertransmitter may calculate the threshold peak frequency value using thereceived reference peak frequency value. As an example, as shown in FIG.27 , the wireless power transmitter may determine a value that is atleast 5 kHz greater than a reference peak frequency fr as a thresholdpeak frequency fth. 5 kHz is a tolerance of the reference peak frequencyvalue, and when a foreign object is present, the foreign object may bedetected by using that a measured peak frequency value which is at leastthe tolerance or more becomes greater than the reference peak frequencyvalue.

The wireless charging method in the wireless power transmitter mayinclude determining whether the measured peak frequency value is greaterthan or equal to the threshold peak frequency value (S2605). Morespecifically, the wireless power transmitter may determine that aforeign object is present when the measured peak frequency value is notgreater than or equal to the threshold peak frequency value. Thewireless power transmitter may perform wireless charging when the peakfrequency value measured in S2605 is not the threshold peak frequencyvalue (S2606). As an example, as shown in FIG. 27 , the measured peakfrequency value of the wireless power transmitter may be a first peakfrequency value f1. Since the first peak frequency value f1 is smallerthan the threshold peak frequency value fth, it is possible to determinethat a foreign object is not present. In this case, since the measuredpeak frequency value is not greater than or equal to the threshold peakfrequency value, the wireless power transmitter determines that aforeign object is present, and may transmit information indicating thatthe foreign object has been detected to the wireless power receiver.

The wireless charging method in the wireless power transmitter mayinclude determining whether the measured equivalent series resistancevalue is less than or equal to the second threshold equivalent seriesresistance value when the measured peak frequency value is greater thanor equal to the threshold peak frequency value (S2607). The wirelesspower transmitter may perform wireless charging when the measured peakfrequency value is greater than or equal to the threshold peak frequencyvalue and the measured equivalent series resistance value is less thanor equal to the second threshold equivalent series resistance value(S2606). The wireless power transmitter may stop wireless charging whenthe measured peak frequency value is greater than or equal to thethreshold peak frequency value and the measured equivalent seriesresistance value is not less than or equal to the second thresholdequivalent series resistance value (S2608). More specifically, when themeasured peak frequency value is greater than or equal to the thresholdpeak frequency value and the measured equivalent series resistance valueis less than or equal to the second threshold equivalent seriesresistance value, the wireless power transmitter determines that aforeign object is not present, and may transmit information indicatingthat the foreign object is not detected to the wireless power receiver.When the measured peak frequency value is greater than or equal to thethreshold peak frequency value and the measured equivalent seriesresistance value is not less than or equal to the second thresholdequivalent series resistance value, the wireless power transmitterdetermines that a foreign object is present, and may transmitinformation indicating that the foreign object has been detected to thewireless power receiver. More specifically, as a charging distancebetween the wireless power transmitter and the wireless power receiverincreases, for example, as a height of the wireless power receiver fromthe wireless power transmitter increases, the peak frequency valuemeasured at the wireless power transmitter increases and the equivalentseries resistance value decreases. When a foreign object is present incharging regions of the wireless power transmitter and the wirelesspower receiver, the peak frequency value increases and the equivalentseries resistance value increases. Therefore, the wireless powertransmitter may determine that the charging distance between thewireless power transmitter and the wireless power receiver is increasedand the foreign object is not present when satisfying all a condition inwhich the measured equivalent series resistance value is low and themeasured peak frequency value is high. Accordingly, the wireless powertransmitter may prevent erroneous recognition that a foreign object ispresent due to an increase in the measured peak frequency value. As anexample, as shown in FIG. 27 , the measured peak frequency value of thewireless power transmitter may be a second peak frequency value f2.Since the second peak frequency value f2 is larger than the thresholdpeak frequency value fth, the second peak frequency value f2 may be asituation in which a foreign object is present or a situation in which acharging distance is increased. At the same time, as shown in FIG. 24 ,the measured equivalent series resistance value of the wireless powertransmitter may be a third equivalent series resistance value ESR3.Since the third equivalent series resistance value ESR3 is smaller thanthe second threshold equivalent series resistance value ESRth2, it maybe determined in the situation in which the charging distance isincreased, not in a situation in which a foreign object is finallypresent.

Therefore, still another embodiment may determine a foreign objectaccurately. In addition, still another embodiment may accuratelydetermine the foreign object to prevent a heat generation phenomenon, adecrease phenomenon in charging efficiency, and a loss of powerconsumption. Yet another embodiment solves a problem in which wirelesscharging is not performed unnecessarily by determining to distinguishthat a charging distance between a wireless power transmitter and awireless power receiver is increased and presence of a foreign object.

FIG. 28 is a view for describing a wireless charging method on awireless charging system according to still another embodiment.

Referring to FIG. 28 , a wireless power transmitter 2810 may transmit ananalog ping to a wireless power receiver 2820 in a selection phase(S2801)

The wireless power transmitter 2810 may measure a quality factor value,an equivalent series resistance value, and a peak frequency value beforea ping phase (S2802). As an example, the wireless power transmitter 2810may measure the equivalent series resistance value in the selectionphase (S2802). The measurement of the peak frequency value may be thesame as the description of FIG. 25 .

The wireless power transmitter 2810 may transit from the selection phaseto the ping phase when an object is sensed. The wireless powertransmitter 2810 may activate the wireless power receiver 2820, and maytransmit a digital ping to identify whether a receiver is the wirelesspower receiver 2820 (S2803). The wireless power receiver 2820 maytransmit a signal strength packet in response to the digital ping(S2804).

When the ping phase is completed, in the identifying and configuringphase, the wireless power receiver 2820 may transmit an identificationpacket to inform the identification information and a configurationpacket to inform the configuration information (S2805 to S2806). Thewireless power transmitter 2810 and the wireless power receiver 2820 maytransition to a negotiation phase when a negotiation field value of theconfiguration packet is a value indicating to perform the negotiationphase.

In the negotiation phase, the wireless power receiver 2820 may transmita FOD status packet for FO detection (S2808). The FOD state packet mayinclude one or more of a reference quality factor value and a referencefrequency value.

The wireless power transmitter 2810 may perform first foreign objectdetection (S2808). The foreign object detection may detect a foreignobject by using any one measured value of the quality factor value andthe equivalent series resistance value, and information of a receivedFOD status packet. The first foreign object detection follows thedescription of the foreign object detection method of FIG. 20 , theforeign object detection method of FIG. 23 , and the wireless chargingmethod of FIG. 29 .

When it is determined that the foreign object is not detected throughthe first foreign object, the wireless power transmitter 2810 mayperform second foreign object detection (S2809). The foreign objectdetection may detect a foreign object by using the measured peakfrequency value and the information of the received FOD state packet.The second foreign object detection follows the description of theforeign object detection method of FIG. 26 and the wireless chargingmethod of FIG. 29 .

The wireless power transmitter 2810 may transmit an ACK to the wirelesspower receiver 2820 in response to the FOD status packet when it isdetermined that the foreign object is not present after performing thesecond foreign object detection (S2810). Conversely, the wireless powertransmitter 2810 may transmit an NAK to the wireless power receiver 2820in response to the FOD status packet when it is determined that theforeign object is present after performing the second foreign objectdetection (S2820).

The wireless power receiver 2820 may transmit a general request packetrequesting a power transmitter capability packet for a powertransmission contract (S2811). The wireless power transmitter 2810 maytransmit the power transmitter capability packet in response to thegeneral request packet (S2812). In this case, a guaranteed power of thepower transmitter capability packet may be a first guaranteed powervalue. A potential power value may be a maximum transmission power valuethat may be transmitted by a wireless power transmitter regardless ofpower limitation due to surrounding requirements. As an example, thefirst guaranteed power value may be a value close to a potential powervalue that is not subject to power limitations due to a number ofwireless power transmitters or a number of wireless power receiversbased on a supply power provided from a power supply of the wirelesspower transmitter. As another example, the first guaranteed power valuemay be a maximum transmission power value that may be transmitted by thewireless power transmitter under conditions (environmental conditions)such as power limitation due to the number of wireless powertransmitters or the number of wireless power receivers. Theenvironmental conditions may refer to a temperature of the transmitter,a capacity of the transmitter's power source, the presence of foreignobject, or influence of friendly metal. The wireless power receiver 2820may transmit a specific request packet to propose the guaranteed powervalue of the power transmission contract based on the first guaranteedpower value of the power transmitter capability packet (S2813). Itshould be noted that the first guaranteed power of the power transmittercapability packet and the guaranteed power of the power transmissioncontract may be distinguished. For example, the wireless power receiver2820 may request a guaranteed power value of the power transmissioncontract with a value equal to or less than the first guaranteed powervalue of the power transmitter capability packet. For convenience ofdescription, the wireless power receiver 2820 requests the guaranteedpower value of the power transmission contract as the same value as thefirst guaranteed power value of the power transmitter capability packet.The wireless power transmitter 2810 may transmit an ACK packet inresponse to a specific request packet for requesting a guaranteed powervalue of the power transmission contract (S2814). That is, the wirelesspower transmitter 2810 is in a case in which the guaranteed power valueof the power transmission contract proposed by the wireless powerreceiver is accepted. That is, the power transmission contract may becompleted with the first guaranteed power value. Thereafter, when thepower transmission contract is completed, the wireless power receiver2820 may transmit a specific request packet for ending the negotiationphase (S2815). The wireless power transmitter 2810 may transmit an ACKpacket in response to the specific request packet for ending thenegotiation phase (S2816). That is, the wireless power transmitter 2810may transmit an ACK packet upon acceptance of the end of the negotiationphase.

In the calibration phase, the wireless power receiver 2820 may transmitthe received power packet to the wireless power transmitter 2810(S2817). In this case, the received power packet may be a 24-bitreceived power packet. The wireless power transmitter 2810 may transmitan ACK packet in response to the received power packet in order toperform wireless charging (S2818).

When the calibration phase is completed, the power transfer phase may beperformed with the first guaranteed power. The wireless power receiver2820 may transmit one or more control error packets in order to controltransmission power of the wireless power transmitter 2810 (S2819). Thewireless power receiver 2820 may transmit the received power packetperiodically or arbitrarily (S2820).

FIG. 29 is a view for describing a wireless charging method in awireless power transmitter according to another embodiment of FIG. 28 .

Referring to FIG. 29 , the wireless charging method in the wirelesspower transmitter according to another embodiment may include sensing anobject in a charging region (S2901). More specifically, the wirelesspower transmitter may sense the object based on a change in current of atransmission coil by transmitting an analog ping.

The wireless charging method in the wireless power transmitter mayinclude measuring a quality factor value, an equivalent seriesresistance value, a peak frequency value before a ping phase (S2902). Asan example, the wireless power transmitter may measure the qualityfactor value using a sensor in a selection phase. In addition, thewireless power transmitter may measure the equivalent series resistancevalue using the sensor in the selection phase. In addition, the wirelesspower transmitter may measure the peak frequency value of transmissionpower using the sensor in the selection phase.

The wireless charging method in the wireless power transmitter mayinclude receiving information including a reference quality factor valueand a reference peak frequency value (S2903). More specifically, thewireless power transmitter may receive an FOD status packet includingthe reference quality factor value and the reference peak frequencyvalue. As an example, the wireless power transmitter may receive the FODstatus packet using a communication unit in a negotiation phase. Thereference quality factor value and the reference peak frequency valueare a quality factor value and a peak frequency value stored in awireless power receiver.

The wireless charging method in the wireless power transmitter mayinclude determining a threshold quality factor value, a first thresholdequivalent series resistance value, a second threshold equivalent seriesresistance value, and a threshold peak frequency value (S2904). A methodof determining the threshold quality factor value may be the same as themethod of determining the threshold quality factor value of FIG. 20 . Inaddition, a method of determining the first threshold equivalent seriesresistance value and the second threshold equivalent series resistancevalue may be the same as the method of determining the first and secondthreshold equivalent series resistance values of FIG. 23 . In addition,a method of determining the threshold peak frequency value may be thesame as the method of determining the threshold peak frequency value ofFIG. 26 .

The wireless charging method in the wireless power transmitter mayinclude detecting a first foreign object (S2905, S2906). As an example,the detecting of the first foreign object may be the same as the foreignobject detection method of FIG. 20 . That is, the wireless powertransmitter may determine that a foreign object is present when ameasured quality factor value is less than or equal to the thresholdquality factor value. As another example, the detecting of the firstforeign object may be the same as the foreign object detection method ofFIG. 23 . That is, the wireless power transmitter may determine that aforeign object is present when a measured equivalent series resistancevalue is greater than or equal to the first threshold equivalent seriesresistance value. When it is determined that a foreign object is presentin S2906, the wireless power transmitter may stop wireless charging(S2907). In this case, the wireless power transmitter determines that aforeign object is present, and may transmit information indicating thatthe foreign object has been detected to the wireless power receiver.

The wireless charging method in the wireless power transmitter mayinclude detecting a second foreign object (S2908, S2909) when it isdetermined that a foreign object is present in the first foreign objectdetection. The detecting of the second foreign object may be the same asthe second foreign object detection method of FIG. 26 . That is, thewireless power transmitter may determine that a foreign object is notpresent when a measured peak frequency value is not greater than orequal to the threshold peak frequency value, or the measured equivalentseries resistance value is less than or equal to the second thresholdequivalent series resistance value, and the measured peak frequencyvalue is greater than or equal to the threshold peak frequency value.When it is determined that a foreign object is not present through thesecond foreign object detection, the wireless power transmitter mayperform wireless charging (S2910). In this case, the wireless powertransmitter may transmit information indicating that the foreign objectis not detected to the wireless power receiver. Conversely, the wirelesspower transmitter may determine that a foreign object is present whenthe measured peak frequency value is greater than or equal to thethreshold peak frequency value and the measured equivalent seriesresistance value is not less than or equal to the second thresholdequivalent series resistance value. When it is determined that a foreignobject is present through the second foreign object detection, thewireless power transmitter may stop wireless charging (S2907). In thiscase, the wireless power transmitter may transmit information indicatingthat the foreign object has been detected to the wireless powerreceiver.

Therefore, still another embodiment may determine a foreign objectaccurately. In addition, still another embodiment may accuratelydetermine the foreign object to prevent a heat generation phenomenon, adecrease phenomenon in charging efficiency, and a loss of powerconsumption. Yet another embodiment solves a problem in which wirelesscharging is not performed unnecessarily by determining to distinguishthat a charging distance between a wireless power transmitter and awireless power receiver is increased and presence of a foreign object.

Methods according to the above-described embodiments may be implementedas a program to be executed by a computer and stored in a computerreadable recording medium. Examples of the computer readable recordingmedium include a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk,an optical data storage device, and the like, and also include what isrealized in the form of carrier wave (for example, transmission throughthe Internet).

The computer readable recording medium may be distributed in computersystems connected via a network and the computer readable code may bestored and executed in a distributed manner. In addition, functionalprograms, codes and code segments for implementing the above-describedmethod may be easily construed by programmers skilled in the art towhich the embodiment pertains.

It will be understood by those skilled in the art that other changes maybe made therein without departing the spirit and features of the presentinvention.

Therefore, the foregoing detailed descriptions are not restrictivelyconstrued in all aspects but have to be considered as illustrativepurposes. The scope of the embodiment has to be determined by rationalinterpretation of appended claims, and all changes within the equivalentscope of the embodiment belong to the scope embodiment.

What is claimed is:
 1. A wireless charging method in a wireless powertransmitter, the method comprising: sensing an object in a chargingregion; measuring a quality factor value; entering a negotiation phaseand receiving a foreign object detection status packet including areference quality factor value; detecting a foreign object using themeasured quality factor value and the reference quality factor value;transmitting a response signal that includes NAK information indicatingthe foreign object is detected; entering a power transfer phaseincluding transmitting information including a second guaranteed powervalue when the response signal includes the NAK information; andentering a renegotiation phase for increasing or decreasing the secondguaranteed power value without receiving an additional foreign objectdetection status packet.
 2. The method of claim 1, further comprising:transmitting a response signal that includes ACK information indicatingthe foreign object is not detected; in the power transfer phase,transmitting information including a first guaranteed power value whenthe response signal includes the ACK information, wherein the firstguaranteed power value is greater than the second guaranteed powervalue; measuring an internal temperature of the wireless powertransmitter; and in the renegotiation phase, transmitting informationincluding a third guaranteed power value when the temperature is lessthan a preset temperature and the response signal includes the NAKinformation, wherein the third guaranteed power value is greater thanthe second guaranteed power value.
 3. The method of claim 2, wherein thesecond guaranteed power value is a minimum guaranteed power of thewireless power transmitter.
 4. The method of claim 1, wherein thedetecting of the foreign object includes: determining a thresholdquality factor value using the reference quality factor value; anddetermining that the foreign object does not exist when the measuredquality factor value is greater than or equal to the threshold qualityfactor value, and determining that the foreign object is present whenthe measured quality factor value is less than the threshold qualityfactor value.
 5. The method of claim 4, wherein the threshold qualityfactor value is a value that is less than the reference quality factorvalue by a first ratio.
 6. The method of claim 1, comprising: comparingthe reference quality factor value with a preset quality factor value ofthe wireless power transmitter; and stopping wireless charging when thereference quality factor value is less than the preset quality factorvalue of the wireless power transmitter.
 7. The method of claim 6,wherein the stopping of the wireless charging is performed when theresponse signal includes the NAK information.
 8. The method of claim 4,wherein the detecting of the foreign object includes stopping wirelesscharging when the measured quality factor value is less than a valuethat is less than the threshold quality factor value by a second ratio.9. The method of claim 8, wherein when the information including thesecond guaranteed power value is transmitted includes when the measuredquality factor value is less than the threshold quality factor value andis greater than a value that is less than the reference quality factorvalue by the second ratio.
 10. The method of claim 2, furthercomprising: in the renegotiation phase, decreasing the second guaranteedpower value when the temperature is greater than or equal to the presettemperature.
 11. The method of claim 2, wherein when the informationincluding the first guaranteed power value is transmitted, a calibrationphase is performed before transitioning to the power transfer phase, andwhen the information including the second guaranteed power value istransmitted, it is transited to the power transfer phase withoutperforming the calibration phase.
 12. The method of claim 11, whereinthe calibration phase includes receiving received power information froma wireless power receiver and determining power loss based on thereceived power information.
 13. The method of claim 11, wherein thepower transfer phase includes receiving a control error signal from awireless power receiver and controlling transmission power.
 14. Awireless power transmitter comprising: an inverter configured to convertDC power into AC power; a transmission coil to which the AC power isapplied; a communication unit configured to demodulate a signalmodulated in a wireless power receiver; a sensor configured to sense avoltage of the transmission coil; and a controller configured to: entera negotiation phase and receive a foreign object detection status packetincluding a reference quality factor value, detect a foreign objectusing the measured quality factor value and the reference quality factorvalue, transmit a response signal that includes NAK informationindicating the foreign object is detected, enter a power transfer phaseincluding transmitting information including a second guaranteed powervalue when the response signal includes the NAK information, and enter arenegotiation phase for increasing or decreasing the second guaranteedpower value without receiving an additional foreign object detectionstatus packet.
 15. The wireless power transmitter of claim 14, whereinthe controller is further configured to: transmit a response signal thatincludes ACK information indicating the foreign object is not detected,in the power transfer phase, transmit information including a firstguaranteed power value when the response signal includes the ACKinformation, wherein the first guaranteed power value is greater thanthe second guaranteed power value, measure an internal temperature ofthe wireless power transmitter, and in the renegotiation phase, transmitinformation including a third guaranteed power value when thetemperature is less than a preset temperature and the response signalincludes the NAK information, and wherein the third guaranteed powervalue is greater than the second guaranteed power value.
 16. Thewireless power transmitter of claim 14, wherein the second guaranteedpower value is a minimum guaranteed power of the wireless powertransmitter.
 17. The wireless power transmitter of claim 14, wherein thecontroller determines a threshold quality factor value using a referencequality factor value constituting the reference factor, determines thatthe foreign object does not exist when the measured quality factor valueis greater than or equal to the threshold quality factor value, anddetermines that the foreign object is present when the measured qualityfactor value is less than the threshold quality factor value.
 18. Thewireless power transmitter of claim 17, wherein the threshold qualityfactor value is a value that is less than the reference quality factorvalue by a first ratio.
 19. The wireless power transmitter of claim 17,wherein the controller compares the reference quality factor valueconstituting the reference factor with a preset quality factor value ofthe wireless power transmitter and stops wireless charging when thereference quality factor value is less than the preset quality factorvalue of the wireless power transmitter.
 20. A wireless power receivercomprising: a receiving coil configured to receive wireless power; arectifier connected to the receiving coil; a converter connected to therectifier; and a controller configured to: sense a voltage output fromthe rectifier and communicate with a wireless power transmitter tocontrol an intensity of power applied to the receiving coil, enter anegotiation phase and transmit a foreign object detection status packetincluding a reference quality factor value, receive a response signalthat includes NAK information indicating a foreign object is detectedbased on a measured quality factor value and the reference qualityfactor value, enter a power transfer phase including receivinginformation including a second guaranteed power value when the responsesignal includes the NAK information, and enter a renegotiation phase forincreasing or decreasing the second guaranteed power value withouttransmitting an additional foreign object detection status packet.